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

Answer 1

I assume you'r talking about the using control block and not the using [namespace] statement. Basically the keyword is syntactic sugar for safely initializing and disposing objects. It works with any object that implements IDisposable. The following:

using(MyType obj = new MyType())
{
  ... do stuff.
}

is equivalent to:

MyType obj = new MyType();
try
{
  .... do stuff
}
finally
{
  if(obj != null)
  {
      obj.Dispose();
  }
}

Answer 2

MSDN is your best bet

http://msdn.microsoft.com/en-us/library/yh598w02%28VS.80%29.aspx

.. but there are plenty of resources out there..

http://blogs.msdn.com/cyrusn/archive/2005/05/10/415956.aspx