.NET with C# chapter 2(variables and data types)

Hierarchy in Visual C#

Namespace à classes à methods

Example

System.Console.WriteLine()

Syntactical rules of Visual C#

1.    All keywords and variables in lower case

2.    All constants in capital

3.    All other items like class name, method name etc. start with capital letter

Every executable C# program must have a class with entry point

1.    static void Main()

2.    static int Main()

3.    

static void Main(string []args)

4.    static int Main(string []args)

Using Visual Studio as Rapid Application Development (RAD) tool

-         Visual Studio 2002

-         Visual Studio 2003

-         Visual Studio 2005

-         Visual Studio 2008

-         Visual Studio 2010

-         Visual Studio 2012

-         Visual Studio 2015

class First

{

    static void Main()

    {

        System.Console.WriteLine("Welcome to C#");

    }

}

Importing the namespace

Use using keyword

Example

using System;

using System;

class First

{

    static void Main()

    {

       Console.WriteLine("Welcome to C#");

    }

}

Creating shortcut or alias

Use using keyword again

Syntax

using <aliasname>=<for what>;

Example

using c=System.Console;

using c = System.Console;

class First

{

    static void Main()

    {

       c.WriteLine("Welcome to C#");

    }

}

.NET provides special built-in structures that represent common data types for all languages called as CTS (Common Type System) provide with .NET Framework as Base Class Library (BCL) provided under System namespace.

·       Byte            1 byte

·       Int16          2 bytes

·       Int32          4 bytes

·       Int64          8 bytes

·       Single         4 bytes float

·       Double       8 bytes float

·       Decimal     16 bytes float

·       Boolean     1 byte

·       Char           2 bytes

All language map these structure with their data types

C#     à     int (4 bytes)                  à Int32

VB     à     Integer (4bytes)            à Int32

using c = System.Console;

using System;

class First

{

    static void Main()

    {

        Int32 n = 5;

        c.WriteLine("Cube root of "+n+" is "+Math.Pow(n,1.0/3));

    }

}

To make program interoperable it must be CLS Compliant. CLS stands for Common Language Specifications.

Data Types in C#

Data type can be of two types

1.    Value type

2.    Reference type

All value types are alias of some structure and created on the stack.

All reference types are alias of some class and created on the heap.

Value Types

1.    byte (unsigned)

2.    short (signed)

3.    int (signed)

4.    long (signed)

5.    sbyte (signed)

6.    ushort (unsigned)

7.    uint (unsigned)

8.    ulong (unsigned)

9.    float

10.                       double

11.                       decimal

12.                       char

13.                       bool

Reference types

1.    string

a.     to hold address of some string

2.    object

a.     to hold address of any type checked at compile time

3.    dynamic

a.     to hold address of any type checked at runtime

Variable Declaration

datatype variablename;

We can also use var keyword to automatically detect type of some data and define the data type automatically also called as infer.

var n=6;

using c = System.Console;

using System;

class First

{

    static void Main()

    {

        var n = 5;

        c.WriteLine(n.GetType());

    }

}