Question

Given,

using (var abc = new Abc())
{

    // abc is not used here at all.

 }

Is it possible the abc is garbage collected before the ending curly brace?

Answer 1

no. internally, there is a reference held to abc until the ending curly brace.

The generated IL code looks like this:

  IL_0001:  newobj     instance void ConsoleApplication1.Abc::.ctor()
  IL_0006:  stloc.0
  .try
  {
    IL_0007:  nop
    IL_0008:  nop
    IL_0009:  leave.s    IL_001b
  }  // end .try
  finally
  {
    IL_000b:  ldloc.0
    IL_000c:  ldnull
    IL_000d:  ceq
    IL_000f:  stloc.1
    IL_0010:  ldloc.1
    IL_0011:  brtrue.s   IL_001a
    IL_0013:  ldloc.0
    IL_0014:  callvirt   instance void [mscorlib]System.IDisposable::Dispose()
    IL_0019:  nop
    IL_001a:  endfinally
  }  // end handler

When the using statement is turned in to IL code, the compiler actually translates that to a full try / finally block, and calls the .Dispose() method on your instance of Abc. So basically it turns it into something like:

Abc abc = new Abc();
try
{
}
finally
{
    abc.Dispose();
}