K MANOHAR GOUD
9866550012
CSHARP FOR BASIC BEGGINERS
C# is a modern, general-purpose object oriented programming language developed by Microsoft and approved by Ecma and 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 to be used on different computer
platforms and architectures.
The following reasons make C# a widely used professional language:
- Modern, general purpose programming language
- Object oriented.
- Component oriented.
- Easy to learn.
- Structured language.
- It produces efficient programs.
- It can be compiled on a variety of computer platforms.
- Part of .Net Framework.
Strong Programming Features of C#
Although C# constructs closely follows 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 multitude of programmers worldwide.
Following is the list of few important features:
- Boolean Conditions
- Automatic Garbage Collection
- Standard Library
- Assembly Versioning
- Properties and Events
- Delegates and Events Management
- Easy to use Generics
- Indexers
- Conditional Compilation
- Simple Multithreading
- LINQ and Lambda Expressions
- Integration with Windows
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 consists of an enormous library of codes used by the client languages like 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
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
Visual C# Express and Visual Web Developer Express edition are trimmed down versions of Visual Studio and has the same look and feel. They retain most features of Visual Studio. In this tutorial, we have used Visual C # 2010 Express.
C# Hello World Example
A C# program basically consists of the following parts:- Namespace declaration
- A class
- Class methods
- Class attributes
- A Main method
- Statements & Expressions
- Comments
using System; namespace HelloWorldApplication { class HelloWorld { static void Main(string[] args) { /* my first program in C# */ Console.WriteLine("Hello World"); Console.ReadKey(); } } }When the above code is compiled and executed, it produces following result:
Hello WorldLet us look at various parts of the above 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 would contain more than one method. 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 will do when executed
- The next line /*...*/ will be ignored by the compiler and it has been put to add additional 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.
- C# is case sensitive.
- All statements and expression must end with a semicolon (;).
- The program execution starts at the Main method.
- Unlike Java, file name could be different from the class name.
Compile & Execute a C# Program:
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.
- Specify a name for your project, and then choose the OK button.
- The new project appears in Solution Explorer.
- Write code in the Code Editor.
- Click the Run button or the F5 key to run the project. A Command Prompt window appears that contains the line Hello World.
- 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 will take you to the next line and would generate helloworld.exe executable file.
- Next, type helloworld to execute your program.
- You will be able to see "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, more often, are said to be in the same class.
For example, let us consider a Rectangle object. It has attributes like 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, on the basis of our observations in it:
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() { 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 following result:
Length: 4.5 Width: 3.5 Area: 15.75
The using Keyword
The first statement in any C# program isusing 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 is used as a class which contains the Main() method and instantiates the Rectangle class.Identifiers
An identifier is a name used to identify a class, variable, function, or any other user-defined 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 the keyword with the @ character.In C# some identifiers have special meaning in context of code, such as get and set, these are called contextual keywords.
In C#, variables are categorized into the following types:
- Value types
- Reference types
- Pointer types
Value Types
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, 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 |
| 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 |
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 following result:
Size of int: 4
Reference Types
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 more than one variable, 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 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. So object types can be assigned values of any other types, value types, reference types, predefined or user-defined 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 runtime.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 take 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";A @quoted string literal looks like:
@"Tutorials Point";The user defined reference types are: class, interface, or delegate. We will discuss these types in later chapter.
Pointer Types
Pointer type variables store the memory address of another type. Pointers in C# have the same capabilities as 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'.
Type conversion is basically type casting, or converting one type of data to another type. In C#, type casting has two forms:
- Implicit type conversion - these conversions are performed by C# in a type-safe manner. Examples are 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.
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 following result:
5673
C# Type Conversion Methods
C# provides the following built-in type conversion methods:| S.N | Methods & Description |
|---|---|
| 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. |
namespace TypeConversionApplication { 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 following result:
75 53.005 2345.7652 True
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.
We have already discussed various data types. 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 |
Variable Declaration in C#
Syntax for variable declaration 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 etc., and variable_list may consist of one or more identifier names separated by commas.
Some valid variable declarations along with their definition are shown here:
int i, j, k; char c, ch; float f, salary; double d; You can initialize a variable at the time of declaration as:
int i = 100;
Variable Initialization in C#
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 (assigned an initial value) 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, sometime program would produce unexpected result.
Try following example which makes use of various types of variables:
namespace VariableDeclaration { class Program { static void Main(string[] args) { short a; int b ; 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 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.
Lvalues and Rvalues in C#:
There are two kinds of expressions in C#:- lvalue : An expression that is an lvalue may appear as either the left-hand or right-hand side of an assignment.
- rvalue : An expression that is an rvalue may appear on the right- but not left-hand side of an assignment.
int g = 20; But following is not a valid statement and would generate compile-time error:
10 = 20;
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 nothing forAn 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 */
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 using 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 e.g., 'x' and can be stored in a simple variable of char type. A character literal can be a plain character (e.g., 'x'), an escape sequence (e.g., '\t'), or a universal character (e.g., '\u02C0').There are certain characters in C# when they are proceeded by a back slash they will have special meaning and they are used to represent like newline (\n) or tab (\t). Here you have 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 |
| \v | Vertical tab |
| \ooo | Octal number of one to three digits |
| \xhh . . . | Hexadecimal number of one or more digits |
namespace EscapeChar { class Program { static void Main(string[] args) { Console.WriteLine("Hello\tWorld\n\n"); Console.ReadLine(); } } }When the above code is compiled and executed, it produces following result:
Hello World
String Literals
String literals or constants are enclosed in double quotes "" or with @"". A string contains characters that are similar to character literals: plain characters, escape sequences, and universal characters.You can break a long line into multiple lines using string literals and separating the parts using whitespaces.
Here are some examples of string literals. All the three forms are identical strings.
"hello, dear" "hello, \ dear" "hello, " "d" "ear" @"hello dear"
Defining Constants
Constants are defined using the const keyword. Syntax for defining a constant is:const <data_type> <constant_name> = value;The following program demonstrates defining and using a constant in your program:
using System; namespace DeclaringConstants { class Program { static void Main(string[] args) { const double pi = 3.14159; // constant declaration double r; Console.WriteLine("Enter Radius: "); r = Convert.ToDouble(Console.ReadLine()); double areaCircle = pi * r * r; Console.WriteLine("Radius: {0}, Area: {1}", r, areaCircle); Console.ReadLine(); } } }When the above code is compiled and executed, it produces following result:
Enter Radius: 3 Radius: 3, Area: 28.27431
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