Question

is it same for the following two code snippets

Snippet 1:

using()
using()
{
   blah blah blah
}

Snippet 2:

using ()
{
  using ()
  {
    blah blah blah
  }
}

Answer 1

They are functionally the same.

See this SO question and answers for some more detail and options for using statements.

using(TypeX x = new TypeX())
using(TypeY y = new TypeY())
{
   blah blah blah
}

Is exactly the same as:

using(TypeX x = new TypeX())
{
  using(TypeY y = new TypeY())
  {
   blah blah blah
  }
}

Also, if your are initializing two variables of the same type, you can do the following:

using(TypeY y1 = new TypeY(), y2 = new TypeY())
{
   blah blah blah
}