Is "Using{}" good practice to dispose object even if there is no variable referring to it

Question

In my company, I am seeing code like this

using (LoggerFactory.GetTracer(_log.ModuleName + "._GetAccessTokenFromWns"))
{...}

When I looked up, I learned it disposes the objects referred by variables declared inside "Using" parenthesis.

Does it also help for code like above, where there is no variable referring to the object returned by the factory?

Thanks,

Answer 1

After I see your question I write a simple code like this:

using (new FileStream("sample.txt",FileMode.CreateNew))
{

}

And then I look at the produced IL code:

    .method private hidebysig static void  Main(string[] args) cil managed
{
  .entrypoint
  // Code size       35 (0x23)
  .maxstack  2
  .locals init ([0] class [mscorlib]System.IO.FileStream CS$3$0000,
           [1] bool CS$4$0001)
  IL_0000:  nop
  IL_0001:  ldstr      "asdas.txt"
  IL_0006:  ldc.i4.1
  IL_0007:  newobj     instance void [mscorlib]System.IO.FileStream::.ctor(string,
                                                                           valuetype [mscorlib]System.IO.FileMode)
  IL_000c:  stloc.0
  .try
  {
    IL_000d:  nop
    IL_000e:  nop
    IL_000f:  leave.s    IL_0021
  }  // end .try
  finally
  {
    IL_0011:  ldloc.0
    IL_0012:  ldnull
    IL_0013:  ceq
    IL_0015:  stloc.1
    IL_0016:  ldloc.1
    IL_0017:  brtrue.s   IL_0020
    IL_0019:  ldloc.0
    IL_001a:  callvirt   instance void [mscorlib]System.IDisposable::Dispose()
    IL_001f:  nop
    IL_0020:  endfinally
  }  // end handler
  IL_0021:  nop
  IL_0022:  ret
} // end of method Program::Main

As you can see it is still calling the Dispose method.It creates FileStream instance before try block, then calling the Dispose method in the finally.I think this is another advantage of using statements.