use of “using” keyword in c# [duplicate]

Answer 1

using keyword can be used to import(Associate) a namspace or library with our program.so that we can use function available in that libraries in our program. Its some thing like a reference

Ex : using System.IO

This means We are going to use some functions present in that library

You can write your own library and import it using the using statement. Ex :

namespace MyProject.MyNamspace
{
 public class MyCustomClass
 {
  public static string MyFunctionToSmile()
  {
   return "He he he heeee";
  }   
}

}

and in ur c# page, use this

using MyProject.MyNamspace

public class MyClass
{
 protected void Page_Load(object sender, EventArgs e)
 {
  Response.Write(MyCustomClass.MyFunctionToSmile());
 } 
}

Cool...!