The using statement defines a scope at the end of which an 
object will be disposed.

How to use
using (expression | type identifier = initializer) statement
where: 

expression 
An expression you want to call Dispose on upon exiting the 
using statement. 

type 
The type of identifier. 

identifier 
The name, or identifier, of the type type. It is possible 
to define more than one identifier of type type. Precede 
each identifier = initializer with a comma. 

initializer 
An expression that creates an object. 

statement 
The embedded statement or statements to executed. 

You create an instance in a using statement to ensure that 
Dispose is called on the object when the using statement is 
exited. A using statement can be exited either when the end 
of the using statement is reached or if, for example, an 
exception is thrown and control leaves the statement block 
before the end of the statement.

The object you instantiate must implement the 
System.IDisposable interface.

Example 
// cs_using_statement.cs
// compile with /reference:System.Drawing.dll
using System.Drawing;
class a
{
   public static void Main()
   {
      using (Font MyFont = new Font("Arial", 10.0f), 
MyFont2 = new Font("Arial", 10.0f))
      {
         // use MyFont and MyFont2
      }   // compiler will call Dispose on MyFont and 
MyFont2

      Font MyFont3 = new Font("Arial", 10.0f);
      using (MyFont3)
      {
         // use MyFont3
      }   // compiler will call Dispose on MyFont3

   }
}
Reference Link: http://msdn2.microsoft.com/en-
us/library/yh598w02(VS.71).aspx