Contents
About the Tutorial ...................................................................................................................................... i
Audience..................................................................................................................................................... i
Prerequisites............................................................................................................................................... i
Disclaimer & Copyright ............................................................................................................................... i
Contents .................................................................................................................................................... ii
1. OVERVIEW............................................................................................................................. 1
Strong Programming Features of C# .......................................................................................................... 1
2. ENVIRONMENT...................................................................................................................... 3
The .Net Framework .................................................................................................................................. 3
Integrated Development Environment (IDE) for C#.................................................................................... 4
Writing C# Programs on Linux or Mac OS................................................................................................... 4
3. PROGRAM STRUCTURE.......................................................................................................... 5
Creating Hello World Program ................................................................................................................... 5
Compiling and Executing the Program ....................................................................................................... 6
C# Keywords ............................................................................................................................................ 10
4. BASIC SYNTAX...................................................................................................................... 12
The using Keyword .................................................................................................................................. 13
The class Keyword ................................................................................................................................... 14
Comments in C#....................................................................................................................................... 14
Member Variables ................................................................................................................................... 14
Member Functions................................................................................................................................... 14
Instantiating a Class ................................................................................................................................. 14
Identifiers ................................................................................................................................................ 15
C# Keywords ............................................................................................................................................ 15
5. DATA TYPES......................................................................................................................... 17
iii
Value Type............................................................................................................................................... 17
Reference Type........................................................................................................................................ 18
Object Type ............................................................................................................................................. 19
Dynamic Type .......................................................................................................................................... 19
String Type............................................................................................................................................... 19
Pointer Type ............................................................................................................................................ 20
6. TYPE CONVERSION .............................................................................................................. 21
C# Type Conversion Methods .................................................................................................................. 22
7. VARIABLES........................................................................................................................... 24
Defining Variables.................................................................................................................................... 24
Initializing Variables................................................................................................................................. 25
Accepting Values from User ..................................................................................................................... 26
Lvalue and Rvalue Expressions in C#: ....................................................................................................... 26
8. CONSTANTS AND LITERALS.................................................................................................. 28
Integer Literals......................................................................................................................................... 28
Floating-point Literals .............................................................................................................................. 29
Character Constants................................................................................................................................. 29
String Literals........................................................................................................................................... 30
Defining Constants................................................................................................................................... 31
9. OPERATORS......................................................................................................................... 33
Arithmetic Operators............................................................................................................................... 33
Relational Operators................................................................................................................................ 35
Logical Operators..................................................................................................................................... 38
Bitwise Operators .................................................................................................................................... 40
Assignment Operators ............................................................................................................................. 43
Miscillaneous Operators .......................................................................................................................... 46
iv
Operator Precedence in C# ...................................................................................................................... 48
10. DECISION MAKING............................................................................................................... 51
if Statement............................................................................................................................................. 52
if...else Statement ................................................................................................................................... 54
The if...else if...else Statement................................................................................................................. 56
Nested if Statements ............................................................................................................................... 58
Switch Statement .................................................................................................................................... 60
The ? : Operator....................................................................................................................................... 65
11. LOOPS ................................................................................................................................. 66
While Loop .............................................................................................................................................. 67
For Loop................................................................................................................................................... 69
Do...While Loop ....................................................................................................................................... 72
Nested Loops ........................................................................................................................................... 75
Loop Control Statements ......................................................................................................................... 78
Infinite Loop ............................................................................................................................................ 83
12. ENCAPSULATION ................................................................................................................. 84
Public Access Specifier ............................................................................................................................. 84
Private Access Specifier ........................................................................................................................... 86
Protected Access Specifier ....................................................................................................................... 88
Internal Access Specifier .......................................................................................................................... 88
13. METHODS............................................................................................................................ 91
Defining Methods in C#............................................................................................................................ 91
Calling Methods in C# .............................................................................................................................. 92
Recursive Method Call ............................................................................................................................. 95
Passing Parameters to a Method ............................................................................................................. 96
Passing Parameters by Value ................................................................................................................... 97
v
Passing Parameters by Reference ............................................................................................................ 99
Passing Parameters by Output............................................................................................................... 100
14. NULLABLES ........................................................................................................................ 104
The Null Coalescing Operator (??).......................................................................................................... 105
15. ARRAYS.............................................................................................................................. 107
Declaring Arrays .................................................................................................................................... 107
Initializing an Array................................................................................................................................ 107
Assigning Values to an Array.................................................................................................................. 108
Accessing Array Elements ...................................................................................................................... 108
Using the foreach Loop .......................................................................................................................... 110
C# Arrays ............................................................................................................................................... 111
Multidimensional Arrays ....................................................................................................................... 112
Two-Dimensional Arrays........................................................................................................................ 112
Jagged Arrays......................................................................................................................................... 115
Passing Arrays as Function Arguments................................................................................................... 117
Param Arrays ......................................................................................................................................... 118
Array Class ............................................................................................................................................. 119
Properties of the Array Class.................................................................................................................. 119
Methods of the Array Class.................................................................................................................... 120
16. STRINGS............................................................................................................................. 124
Creating a String Object ......................................................................................................................... 124
Properties of the String Class ................................................................................................................. 126
Methods of the String Class ................................................................................................................... 126
17. STRUCTURES ..................................................................................................................... 135
Defining a Structure............................................................................................................................... 135
Features of C# Structures....................................................................................................................... 137
vi
Class versus Structure ............................................................................................................................ 138
18. ENUMS.............................................................................................................................. 141
Declaring enum Variable ........................................................................................................................ 141
19. CLASSES............................................................................................................................. 143
Defining a Class...................................................................................................................................... 143
Member Functions and Encapsulation ................................................................................................... 145
C# Constructors ..................................................................................................................................... 148
C# Destructors ....................................................................................................................................... 151
Static Members of a C# Class ................................................................................................................. 152
20. INHERITANCE..................................................................................................................... 156
Base and Derived Classes....................................................................................................................... 156
Initializing Base Class ............................................................................................................................. 158
Multiple Inheritance in C#...................................................................................................................... 160
21. POLYMORPHISM................................................................................................................ 163
Static Polymorphism.............................................................................................................................. 163
Dynamic Polymorphism ......................................................................................................................... 165
22. OPERATOR OVERLOADING ................................................................................................ 170
Implementing the Operator Overloading............................................................................................... 170
Overloadable and Non-Overloadable Operators.................................................................................... 173
23. INTERFACES....................................................................................................................... 181
Declaring Interfaces ............................................................................................................................... 181
24. NAMESPACES .................................................................................................................... 184
Defining a Namespace ........................................................................................................................... 184
The using Keyword................................................................................................................................. 185
Nested Namespaces............................................................................................................................... 187
vii
25. PREPROCESSOR DIRECTIVES .............................................................................................. 190
Preprocessor Directives in C#................................................................................................................. 190
The #define Preprocessor ...................................................................................................................... 191
Conditional Directives............................................................................................................................ 192
26. REGULAR EXPRESSIONS..................................................................................................... 194
Constructs for Defining Regular Expressions .......................................................................................... 194
Character Escapes.................................................................................................................................. 194
Character Classes ................................................................................................................................... 196
Grouping Constructs .............................................................................................................................. 198
Quantifier .............................................................................................................................................. 199
Backreference Constructs ...................................................................................................................... 200
Alternation Constructs........................................................................................................................... 201
Substitution ........................................................................................................................................... 202
Miscellaneous Constructs ...................................................................................................................... 202
The Regex Class ..................................................................................................................................... 203
27. EXCEPTION HANDLING ...................................................................................................... 208
Exception Classes in C# .......................................................................................................................... 209
Handling Exceptions .............................................................................................................................. 210
Creating User-Defined Exceptions.......................................................................................................... 212
Throwing Objects................................................................................................................................... 213
28. FILE I/O.............................................................................................................................. 214
C# I/O Classes ........................................................................................................................................ 214
The FileStream Class .............................................................................................................................. 215
Advanced File Operations in C# ............................................................................................................. 217
Reading from and Writing to Text Files .................................................................................................. 218
The StreamReader Class ........................................................................................................................ 218
The StreamWriter Class ......................................................................................................................... 220
viii
Reading from and Writing into Binary files ............................................................................................ 222
The BinaryWriter Class........................................................................................................................... 224
Windows File System ............................................................................................................................. 228
The DirectoryInfo Class .......................................................................................................................... 228
The FileInfo Class ................................................................................................................................... 230
29. ATTRIBUTES....................................................................................................................... 234
Specifying an Attribute .......................................................................................................................... 234
Predefined Attributes ............................................................................................................................ 234
AttributeUsage ...................................................................................................................................... 234
Conditional ............................................................................................................................................ 235
Obsolete ................................................................................................................................................ 237
Creating Custom Attributes ................................................................................................................... 238
Constructing the Custom Attribute ........................................................................................................ 239
Applying the Custom Attribute .............................................................................................................. 241
30. REFLECTION....................................................................................................................... 243
Applications of Reflection ...................................................................................................................... 243
Viewing Metadata ................................................................................................................................. 243
31. PROPERTIES....................................................................................................................... 251
Accessors ............................................................................................................................................... 251
Abstract Properties................................................................................................................................ 255
32. INDEXERS .......................................................................................................................... 259
Use of Indexers ...................................................................................................................................... 259
Overloaded Indexers.............................................................................................................................. 262
33. DELEGATES........................................................................................................................ 266
Declaring Delegates ............................................................................................................................... 266
Instantiating Delegates .......................................................................................................................... 266
ix
Multicasting of a Delegate ..................................................................................................................... 268
Using Delegates .................................................................................................................................... 270
34. EVENTS.............................................................................................................................. 272
Using Delegates with Events .................................................................................................................. 272
Declaring Events .................................................................................................................................... 272
35. COLLECTIONS .................................................................................................................... 279
ArrayList Class........................................................................................................................................ 280
Hashtable Class...................................................................................................................................... 284
SortedList Class...................................................................................................................................... 288
Stack Class ............................................................................................................................................. 292
Queue Class ........................................................................................................................................... 295
BitArray Class......................................................................................................................................... 297
36. GENERICS .......................................................................................................................... 302
Features of Generics .............................................................................................................................. 304
Generic Methods ................................................................................................................................... 304
Generic Delegates.................................................................................................................................. 306
37. ANONYMOUS METHODS ................................................................................................... 309
Writing an Anonymous Method............................................................................................................. 309
38. UNSAFE CODES.................................................................................................................. 312
Pointers ................................................................................................................................................. 312
Retrieving the Data Value Using a Pointer ............................................................................................. 313
Passing Pointers as Parameters to Methods .......................................................................................... 314
Accessing Array Elements Using a Pointer ............................................................................................. 315
Compiling Unsafe Code.......................................................................................................................... 316
39. MULTITHREADING............................................................................................................. 318
Thread Life Cycle.................................................................................................................................... 318
x
Properties and Methods of the Thread Class ......................................................................................... 319
Creating Threads.................................................................................................................................... 323
Managing Threads ................................................................................................................................. 324
Destroying Threads................................................................................................................................ 326
1
C# is a modern, general-purpose, object-oriented programming language developed
by Microsoft and approved by European Computer Manufacturers Association (ECMA)
and International Standards Organization (ISO).
C# was developed by Anders Hejlsberg and his team during the development of .Net
Framework.
C# is designed for Common Language Infrastructure (CLI), which consists of the
executable code and runtime environment that allows use of various high-level
languages on different computer platforms and architectures.
The following reasons make C# a widely used professional language:
 It is a modern, general-purpose programming language
 It is object oriented.
 It is component oriented.
 It is easy to learn.
 It is a tructured language.
 It produces efficient programs.
 It can be compiled on a variety of computer platforms.
 It is a part of .Net Framework.
Strong Programming Features of C#
Although C# constructs closely follow traditional high-level languages, C and C++
and being an object-oriented programming language. It has strong resemblance with
Java, it has numerous strong programming features that make it endearing to a
number of programmers worldwide.
Following is the list of few important features of C#:
 Boolean Conditions
 Automatic Garbage Collection
 Standard Library
 Assembly Versioning
 Properties and Events
 Delegates and Events Management
 Easy-to-use Generics
 Indexers
1. OVERVIEW
2
 Conditional Compilation
 Simple Multithreading
 LINQ and Lambda Expressions
 Integration with Windows
3
In this chapter, we will discuss the tools required for creating C# programming. We
have already mentioned that C# is part of .Net framework and is used for writing
.Net applications. Therefore, before discussing the available tools for running a C#
program, let us understand how C# relates to the .Net framework.
The .Net Framework
The .Net framework is a revolutionary platform that helps you to write the following
types of applications:
 Windows applications
 Web applications
 Web services
The .Net framework applications are multi-platform applications. The framework has
been designed in such a way that it can be used from any of the following languages:
C#, C++, Visual Basic, Jscript, COBOL, etc. All these languages can access the
framework as well as communicate with each other.
The .Net framework consists of an enormous library of codes used by the client
languages such as C#. Following are some of the components of the .Net framework:
 Common Language Runtime (CLR)
 The .Net Framework Class Library
 Common Language Specification
 Common Type System
 Metadata and Assemblies
 Windows Forms
 ASP.Net and ASP.Net AJAX
 ADO.Net
 Windows Workflow Foundation (WF)
 Windows Presentation Foundation
 Windows Communication Foundation (WCF)
 LINQ
For the jobs each of these components perform, please see ASP.Net - Introduction, and
for details of each component, please consult Microsoft's documentation.
2. ENVIRONMENT
4
Integrated Development Environment (IDE) for C#
Microsoft provides the following development tools for C# programming:
 Visual Studio 2010 (VS)
 Visual C# 2010 Express (VCE)
 Visual Web Developer
The last two are freely available from Microsoft official website. Using these tools,
you can write all kinds of C# programs from simple command-line applications to
more complex applications. You can also write C# source code files using a basic text
editor like Notepad, and compile the code into assemblies using the command-line
compiler, which is again a part of the .NET Framework.
Visual C# Express and Visual Web Developer Express edition are trimmed down
versions of Visual Studio and has the same appearance. They retain most features of
Visual Studio. In this tutorial, we have used Visual C# 2010 Express.
You can download it from Microsoft Visual Studio. It gets installed automatically on your
machine.
Note: You need an active internet connection for installing the express edition.
Writing C# Programs on Linux or Mac OS
Although the.NET Framework runs on the Windows operating system, there are some
alternative versions that work on other operating systems. Mono is an open-source
version of the .NET Framework which includes a C# compiler and runs on several
operating systems, including various flavors of Linux and Mac OS. Kindly check Go
Mono.
The stated purpose of Mono is not only to be able to run Microsoft .NET applications
cross-platform, but also to bring better development tools for Linux developers. Mono
can be run on many operating systems including Android, BSD, iOS, Linux, OS X,
Windows, Solaris, and UNIX.
5
Before we study basic building blocks of the C# programming language, let us look
at a bare minimum C# program structure so that we can take it as a reference in
upcoming chapters.
Creating Hello World Program
A C# program consists of the following parts:
 Namespace declaration
 A class
 Class methods
 Class attributes
 A Main method
 Statements and Expressions
 Comments
Let us look at a simple code that prints the words "Hello World":
using System;
namespace HelloWorldApplication
{
class HelloWorld
{
static void Main(string[] args)
{
/* my first program in C# */
Console.WriteLine("Hello World");
Console.ReadKey();
}
}
}
3. PROGRAM STRUCTURE
6
When this code is compiled and executed, it produces the following result:
Hello World
Let us look at the various parts of the given program:
 The first line of the program using System; - the using keyword is used to
include the System namespace in the program. A program generally has
multiple using statements.
 The next line has the namespace declaration. A namespace is a collection of
classes. The HelloWorldApplication namespace contains the class HelloWorld.
 The next line has a class declaration, the class HelloWorld contains the data
and method definitions that your program uses. Classes generally contain
multiple methods. Methods define the behavior of the class. However, the
HelloWorld class has only one method Main.
 The next line defines the Main method, which is the entry point for all C#
programs. The Main method states what the class does when executed.
 The next line /*...*/ is ignored by the compiler and it is put to add
comments in the program.
 The Main method specifies its behavior with the statement
Console.WriteLine("Hello World");
 WriteLine is a method of the Console class defined in the System namespace.
This statement causes the message "Hello, World!" to be displayed on the
screen.
 The last line Console.ReadKey(); is for the VS.NET Users. This makes the
program wait for a key press and it prevents the screen from running and
closing quickly when the program is launched from Visual Studio .NET.
It is worth to note the following points:
 C# is case sensitive.
 All statements and expression must end with a semicolon (;).
 The program execution starts at the Main method.
 Unlike Java, program file name could be different from the class name.
Compiling andExecuting theProgram
If you are using Visual Studio.Net for compiling and executing C# programs, take the
following steps:
 Start Visual Studio.
 On the menu bar, choose File -> New -> Project.
 Choose Visual C# from templates, and then choose Windows.
 Choose Console Application.
7
 Specify a name for your project and click OK button. This creates a new project
in Solution Explorer.
 Write code in the Code Editor.
 Click the Run button or press F5 key to execute the project. A Command
Prompt window appears that contains the line Hello World.
You can compile a C# program by using the command-line instead of the Visual
Studio IDE:
 Open a text editor and add the above-mentioned code.
 Save the file as helloworld.cs
 Open the command prompt tool and go to the directory where you saved the
file.
 Type csc helloworld.cs and press enter to compile your code.
 If there are no errors in your code, the command prompt takes you to the next
line and generates helloworld.exe executable file.
 Type helloworld to execute your program.
 You can see the output Hello World printed on the screen.
C# is an object-oriented programming language. In Object-Oriented Programming
methodology, a program consists of various objects that interact with each other by
means of actions. The actions that an object may take are called methods. Objects
of the same kind are said to have the same type or are said to be in the same class.
For example, let us consider a Rectangle object. It has attributes such as length and
width. Depending upon the design, it may need ways for accepting the values of
these attributes, calculating the area, and displaying details.
Let us look at implementation of a Rectangle class and discuss C# basic syntax:
using System;
namespace RectangleApplication
{
class Rectangle
{
// member variables
double length;
double width;
public void Acceptdetails()
{
length = 4.5;
8
width = 3.5;
}
public double GetArea()
{
return length * width;
}
public void Display()
{
Console.WriteLine("Length: {0}", length);
Console.WriteLine("Width: {0}", width);
Console.WriteLine("Area: {0}", GetArea());
}
}
class ExecuteRectangle
{
static void Main(string[] args)
{
Rectangle r = new Rectangle();
r.Acceptdetails();
r.Display();
Console.ReadLine();
}
}
}
When the above code is compiled and executed, it produces the following result:
Length: 4.5
9
Width: 3.5
Area: 15.75
The using Keyword
The first statement in any C# program is
using System;
The using keyword is used for including the namespaces in the program. A program
can include multiple using statements.
The class Keyword
The class keyword is used for declaring a class.
Comments in C#
Comments are used for explaining code. Compilers ignore the comment entries. The
multiline comments in C# programs start with /* and terminates with the characters
*/ as shown below:
/* This program demonstrates
The basic syntax of C# programming
Language */
Single-line comments are indicated by the '//' symbol. For example,
}//end class Rectangle
Member Variables
Variables are attributes or data members of a class, used for storing data. In the
preceding program, the Rectangle class has two member variables
named length and width.
Member Functions
Functions are set of statements that perform a specific task. The member functions
of a class are declared within the class. Our sample class Rectangle contains three
member functions: AcceptDetails, GetArea and Display.
Instantiating a Class
In the preceding program, the class ExecuteRectangle contains the Main() method
and instantiates the Rectangle class.
Identifiers
10
An identifier is a name used to identify a class, variable, function, or any other userdefined item. The basic rules for naming classes in C# are as follows:
 A name must begin with a letter that could be followed by a sequence of letters,
digits (0 - 9) or underscore. The first character in an identifier cannot be a
digit.
 It must not contain any embedded space or symbol such as ? - +! @ # % ^ &
* ( ) [ ] { } . ; : " ' / and \. However, an underscore ( _ ) can be used.
 It should not be a C# keyword.
C# Keywords
Keywords are reserved words predefined to the C# compiler. These keywords cannot
be used as identifiers. However, if you want to use these keywords as identifiers, you
may prefix the keyword with the @ character.
In C#, some identifiers have special meaning in context of code, such as get and set
are called contextual keywords.
The following table lists the reserved keywords and contextual keywords in C#:
Reserved Keywords
abstract as base bool break byte case
catch char checked class const continue decimal
default delegate do double else enum event
explicit extern false finally fixed float for
foreach goto if implicit In in (generic modifier) int
interface internal is lock long namespace new
null object operator out
out
(generic
modifier)
override params
private protected public readonly ref return sbyte
sealed short sizeof stackalloc static string struct
switch this throw true try typeof uint
ulong unchecked unsafe ushort using virtual void
volatile while
11
Contextual Keywords
add alias ascending descending dynamic from get
global group into join let orderby partial
(type)
partial
(method) remove select set
12
C# is an object-oriented programming language. In Object-Oriented Programming
methodology, a program consists of various objects that interact with each other by
means of actions. The actions that an object may take are called methods. Objects
of the same kind are said to have the same type or, more often, are said to be in the
same class.
For example, let us consider an object Rectangle. It has attributes such as length and
width. Depending upon the design, it may need ways for accepting the values of
these attributes, calculating area, and display details.
Let us look at an implementation of a Rectangle class and discuss C# basic syntax:
using System;
namespace RectangleApplication
{
class Rectangle
{
// member variables
double length;
double width;
public void Acceptdetails()
{
length = 4.5;
width = 3.5;
}
public double GetArea()
{
return length * width;
}
public void Display()
4. BASIC SYNTAX
13
{
Console.WriteLine("Length: {0}", length);
Console.WriteLine("Width: {0}", width);
Console.WriteLine("Area: {0}", GetArea());
}
}
class ExecuteRectangle
{
static void Main(string[] args)
{
Rectangle r = new Rectangle();
r.Acceptdetails();
r.Display();
Console.ReadLine();
}
}
}
When the above code is compiled and executed, it produces the following result:
Length: 4.5
Width: 3.5
Area: 15.75
Theusing Keyword
The first statement in any C# program is -
using System;
14
The using keyword is used for including the namespaces in the program. A program
can include multiple using statements.
The class Keyword
The class keyword is used for declaring a class.
Comments in C#
Comments are used for explaining code. Compiler ignores the comment entries. The
multiline comments in C# programs start with /* and terminates with the characters
*/ as shown below:
/* This program demonstrates
The basic syntax of C# programming
Language */
Single-line comments are indicated by the '//' symbol. For example,
}//end class Rectangle
Member Variables
Variables are attributes or data members of a class. They are used for storing data.
In the preceding program, the Rectangle class has two member variables
named length and width.
MemberFunctions
Functions are set of statements that perform a specific task. The member functions
of a class are declared within the class. Our sample class Rectangle contains three
member functions: AcceptDetails, GetArea, and Display.
Instantiating a Class
In the preceding program, the class ExecuteRectangle is used as a class, which
contains the Main() method and instantiates the Rectangle class.
15
Identifiers
An identifier is a name used to identify a class, variable, function, or any other userdefined item. The basic rules for naming classes in C# are as follows:
 A name must begin with a letter that could be followed by a sequence of letters,
digits (0 - 9), or underscore. The first character in an identifier cannot be a
digit.
 It must not contain any embedded space or symbol like ? - +! @ # % ^ & * (
) [ ] { } . ; : " ' / and \. However, an underscore ( _ ) can be used.
 It should not be a C# keyword.
C# Keywords
Keywords are reserved words predefined to the C# compiler. These keywords cannot
be used as identifiers. However, if you want to use these keywords as identifiers, you
may prefix them with the @ character.
In C#, some identifiers have special meaning in context of code, such as get and set,
these are called contextual keywords.
The following table lists the reserved keywords and contextual keywords in C#:
Reserved Keywords
abstract as base bool break byte case
catch char checked class const continue decimal
default delegate do double else enum event
explicit extern false finally fixed float for
foreach goto if implicit in in (generic
modifier) int
interface internal is lock long namespace new
null object operator out
out
(generic
modifier)
override params
private protected public readonly ref return sbyte
16
sealed short sizeof stackalloc static string struct
switch this throw true try typeof uint
ulong unchecked unsafe ushort using virtual void
volatile while
Contextual Keywords
add alias ascending descending dynamic from get
global group into join let orderby partial
(type)
partial
(method) remove select set
17
The variables in C#, are categorized into the following types:
 Value types
 Reference types
 Pointer types
Value Type
Value type variables can be assigned a value directly. They are derived from the class
System.ValueType.
The value types directly contain data. Some examples are int, char, and float, which
stores numbers, alphabets, and floating point numbers, respectively. When you
declare an int type, the system allocates memory to store the value.
The following table lists the available value types in C# 2010:
Type Represents Range Default
Value
bool Boolean value True or False False
byte 8-bit unsigned integer 0 to 255 0
char 16-bit Unicode character U +0000 to U +ffff '\0'
decimal
128-bit precise decimal
values with 28-29
significant digits
(-7.9 x 1028 to 7.9 x 1028) / 100 to 28 0.0M
double 64-bit double-precision
floating point type (+/-)5.0 x 10-324 to (+/-)1.7 x 10308 0.0D
float 32-bit single-precision
floating point type -3.4 x 1038 to + 3.4 x 1038 0.0F
Int 32-bit signed integer type -2,147,483,648 to 2,147,483,647 0
long 64-bit signed integer type -923,372,036,854,775,808 to
9,223,372,036,854,775,807 0L
sbyte 8-bit signed integer type -128 to 127 0
5. DATA TYPES
18
short 16-bit signed integer type -32,768 to 32,767 0
uint 32-bit unsigned integer
type 0 to 4,294,967,295 0
ulong 64-bit unsigned integer
type 0 to 18,446,744,073,709,551,615 0
ushort 16-bit unsigned integer
type 0 to 65,535 0
To get the exact size of a type or a variable on a particular platform, you can use
the sizeof method. The expression sizeof(type) yields the storage size of the object
or type in bytes. Following is an example to get the size of int type on any machine:
namespace DataTypeApplication
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Size of int: {0}", sizeof(int));
Console.ReadLine();
}
}
}
When the above code is compiled and executed, it produces the following result:
Size of int: 4
Reference Type
The reference types do not contain the actual data stored in a variable, but they
contain a reference to the variables.
In other words, they refer to a memory location. Using multiple variables, the
reference types can refer to a memory location. If the data in the memory location
is changed by one of the variables, the other variable automatically reflects this
19
change in value. Example of built-in reference types
are: object, dynamic, and string.
Object Type
The Object Type is the ultimate base class for all data types in C# Common Type
System (CTS). Object is an alias for System.Object class. The object types can be
assigned values of any other types, value types, reference types, predefined or userdefined types. However, before assigning values, it needs type conversion.
When a value type is converted to object type, it is called boxing and on the other
hand, when an object type is converted to a value type, it is called unboxing.
object obj;
obj = 100; // this is boxing
Dynamic Type
You can store any type of value in the dynamic data type variable. Type checking for
these types of variables takes place at run-time.
Syntax for declaring a dynamic type is:
dynamic <variable_name> = value;
For example,
dynamic d = 20;
Dynamic types are similar to object types except that type checking for object type
variables takes place at compile time, whereas that for the dynamic type variables
takes place at run time.
String Type
The String Type allows you to assign any string values to a variable. The string type
is an alias for the System.String class. It is derived from object type. The value for a
string type can be assigned using string literals in two forms: quoted and @quoted.
For example,
String str = "Tutorials Point";
20
A @quoted string literal looks as follows:
@"Tutorials Point";
The user-defined reference types are: class, interface, or delegate. We will discuss
these types in later chapter.
Pointer Type
Pointer type variables store the memory address of another type. Pointers in C# have
the same capabilities as the pointers in C or C++.
Syntax for declaring a pointer type is:
type* identifier;
For example,
char* cptr;
int* iptr;
We will discuss pointer types in the chapter 'Unsafe Codes'.
21
Type conversion is converting one type of data to another type. It is also known as
Type Casting. In C#, type casting has two forms:
 Implicit type conversion - These conversions are performed by C# in a typesafe manner. For example, conversions from smaller to larger integral types
and conversions from derived classes to base classes.
 Explicit type conversion - These conversions are done explicitly by users
using the pre-defined functions. Explicit conversions require a cast operator.
The following example shows an explicit type conversion:
using System;
namespace TypeConversionApplication
{
class ExplicitConversion
{
static void Main(string[] args)
{
double d = 5673.74;
int i;
// cast double to int.
i = (int)d;
Console.WriteLine(i);
Console.ReadKey();
}
}
}
When the above code is compiled and executed, it produces the following result:
6. TYPE CONVERSION
22
5673
C# Type Conversion Methods
C# provides the following built-in type conversion methods as described:
Sr. No. Methods
1 ToBoolean
Converts a type to a Boolean value, where possible.
2 ToByte
Converts a type to a byte.
3 ToChar
Converts a type to a single Unicode character, where possible.
4 ToDateTime
Converts a type (integer or string type) to date-time structures.
5 ToDecimal
Converts a floating point or integer type to a decimal type.
6 ToDouble
Converts a type to a double type.
7 ToInt16
Converts a type to a 16-bit integer.
8 ToInt32
Converts a type to a 32-bit integer.
9 ToInt64
Converts a type to a 64-bit integer.
10 ToSbyte
Converts a type to a signed byte type.
11 ToSingle
Converts a type to a small floating point number.
12 ToString
Converts a type to a string.
13 ToType
Converts a type to a specified type.
14 ToUInt16
Converts a type to an unsigned int type.
15 ToUInt32
Converts a type to an unsigned long type.
16 ToUInt64
Converts a type to an unsigned big integer.
The following example converts various value types to string type:
namespace TypeConversionApplication
23
{
class StringConversion
{
static void Main(string[] args)
{
int i = 75;
float f = 53.005f;
double d = 2345.7652;
bool b = true;
Console.WriteLine(i.ToString());
Console.WriteLine(f.ToString());
Console.WriteLine(d.ToString());
Console.WriteLine(b.ToString());
Console.ReadKey();
}
}
}
When the above code is compiled and executed, it produces the following result:
75
53.005
2345.7652
True
24
A variable is nothing but a name given to a storage area that our programs can
manipulate. Each variable in C# has a specific type, which determines the size and
layout of the variable's memory, the range of values that can be stored within that
memory, and the set of operations that can be applied to the variable.
The basic value types provided in C# can be categorized as:
Type Example
Integral types sbyte, byte, short, ushort, int, uint, long, ulong, and char
Floating point types float and double
Decimal types decimal
Boolean types true or false values, as assigned
Nullable types Nullable data types
C# also allows defining other value types of variablesuch as enum and reference
types of variablessuch as class, which we will cover in subsequent chapters.
DefiningVariables
Syntax for variable definition in C# is:
<data_type> <variable_list>;
Here, data_type must be a valid C# data type including char, int, float, double, or
any user-defined data type, and variable_list may consist of one or more identifier
names separated by commas.
Some valid variable definitions are shown here:
int i, j, k;
char c, ch;
float f, salary;
7. VARIABLES
25
double d;
You can initialize a variable at the time of definition as:
int i = 100;
Initializing Variables
Variables are initialized (assigned a value) with an equal sign followed by a constant
expression. The general form of initialization is:
variable_name = value;
Variables can be initialized in their declaration. The initializer consists of an equal sign
followed by a constant expression as:
<data_type> <variable_name> = value;
Some examples are:
int d = 3, f = 5; /* initializing d and f. */
byte z = 22; /* initializes z. */
double pi = 3.14159; /* declares an approximation of pi. */
char x = 'x'; /* the variable x has the value 'x'. */
It is a good programming practice to initialize variables properly, otherwise
sometimes program may produce unexpected result.
The following example uses various types of variables:
using System;
namespace VariableDefinition
{
class Program
{
static void Main(string[] args)
{
short a;
int b ;
26
double c;
/* actual initialization */
a = 10;
b = 20;
c = a + b;
Console.WriteLine("a = {0}, b = {1}, c = {2}", a, b, c);
Console.ReadLine();
}
}
}
When the above code is compiled and executed, it produces the following result:
a = 10, b = 20, c = 30
Accepting Values from User
The Console class in the System namespace provides a function ReadLine() for
accepting input from the user and store it into a variable.
For example,
int num;
num = Convert.ToInt32(Console.ReadLine());
The function Convert.ToInt32() converts the data entered by the user to int data
type, because Console.ReadLine() accepts the data in string format.
Lvalue and RvalueExpressionsin C#:
There are two kinds of expressions in C#:
1. lvalue: An expression that is an lvalue may appear as either the left-hand or
right-hand side of an assignment.
2. rvalue: An expression that is an rvalue may appear on the right- but not lefthand side of an assignment.
27
Variables are lvalues and hence they may appear on the left-hand side of an
assignment. Numeric literals are rvalues and hence they may not be assigned and
can not appear on the left-hand side. Following is a valid C# statement:
int g = 20;
But following is not a valid statement and would generate compile-time error:
10 = 20;
28
The constants refer to fixed values that the program may not alter during its
execution. These fixed values are also called literals. Constants can be of any of the
basic data types like an integer constant, a floating constant, a character constant,
or a string literal. There are also enumeration constants as well.
The constants are treated just like regular variables except that their values cannot
be modified after their definition.
Integer Literals
An integer literal can be a decimal, octal, or hexadecimal constant. A prefix specifies
the base or radix: 0x or 0X for hexadecimal, 0 for octal, and no prefix id for decimal.
An integer literal can also have a suffix that is a combination of U and L, for unsigned
and long, respectively. The suffix can be uppercase or lowercase and can be in any
order.
Here are some examples of integer literals:
212 /* Legal */
215u /* Legal */
0xFeeL /* Legal */
078 /* Illegal: 8 is not an octal digit */
032UU /* Illegal: cannot repeat a suffix */
Following are other examples of various types of Integer literals:
85 /* decimal */
0213 /* octal */
0x4b /* hexadecimal */
30 /* int */
30u /* unsigned int */
30l /* long */
30ul /* unsigned long */
8. CONSTANTS AND LITERALS
29
Floating-point Literals
A floating-point literal has an integer part, a decimal point, a fractional part, and an
exponent part. You can represent floating point literals either in decimal form or
exponential form.
Here are some examples of floating-point literals:
3.14159 /* Legal */
314159E-5L /* Legal */
510E /* Illegal: incomplete exponent */
210f /* Illegal: no decimal or exponent */
.e55 /* Illegal: missing integer or fraction */
While representing in decimal form, you must include the decimal point, the
exponent, or both; and while representing using exponential form you must include
the integer part, the fractional part, or both. The signed exponent is introduced by e
or E.
Character Constants
Character literals are enclosed in single quotes. For example, 'x' and can be stored
in a simple variable of char type. A character literal can be a plain character (such as
'x'), an escape sequence (such as '\t'), or a universal character (such as '\u02C0').
There are certain characters in C# when they are preceded by a backslash. They
have special meaning and they are used to represent like newline (\n) or tab (\t).
Here, is a list of some of such escape sequence codes:
Escape sequence Meaning
\\ \ character
\' ' character
\" " character
\? ? character
\a Alert or bell
\b Backspace
\f Form feed
\n Newline
\r Carriage return
\t Horizontal tab
30
\v Vertical tab
\ooo Octal number of one to three digits
\xhh . . . Hexadecimal number of one or more digits
Following is the example to show few escape sequence character