C#

Christian Graus wrote:

The unmanaged objects are released right away, that's how Dispose always works.

Christian Graus wrote:

The GC will remove the object, as all references have expired.

Christian Graus wrote:

At this point, Finalise is called, which should clean up the same stuff Dispose does, you call Dispose to have stuff cleared without waiting for GC.

lmoelleb wrote:

If you forgot to call Dispose it will still be called from the garbage collector when it gets arround to release the object.

MSDN says:

Do not assume that Dispose will be called. Unmanaged resources owned by a type should also be released in a Finalize method in the event that Dispose is not called.

<br />
class Whatever : IDisposable<br />
{<br />
  ~Whatever<br />
  {<br />
    // this is NOT calling Dispose as per MSDN instructions,<br />
    // but an overload of Dispose that could<br />
    // as well have been named something else (naming it<br />
    // Dispose(bool) is that standard though, so it would be confusing<br />
    // to deviate from it).<br />
    Dispose(false); <br />
  }<br />
<br />
  public void Dispose()<br />
  {<br />
    Dispose(true);<br />
  }<br />
<br />
  private void Dispose(bool disposing)<br />
  {<br />
    // TODO: Release any unmanaged references here (so no matter if<br />
    // it is a Dispose or finalizer call.<br />
    if (disposing)<br />
    {<br />
      // This is only executed when Dispose is called, not when called<br />
      // though the finalizer.<br />
<br />
      // TODO: Dispose referenced managed objects here if any of them<br />
      // implements IDisposable. Never ever try to release them from<br />
      // the finalizer call - they might already have been released.<br />
<br />
      // Tell the Garbage Collector it no longer need to finalize this, if<br />
      // this isn't done, the object will end up being promoted a generation<br />
      // before being released.<br />
      GC.SuppressFinalize(this)<br />
    }<br />
  }<br />
}<br />

lmoelleb wrote:

No, the GC will never call Dispose, hence the need for the finalizer in the first place.

lmoelleb wrote:

Yes, a finalizer can impact performance - as I wrote in a comment in my example a finalizer will force the object to be promoted a generation in the garbage collector before it is released (which does not matter if it is a single object you dispose when closing the application, but for something you use a lot it is a problem).

lmoelleb wrote:

However you will see that the call to Dispose result in a call to GC.SuppressFinalize(this) which basically disable the finalizer for the object once it has been Disposed (as we have cleaned up the references no need to call it again). This elimintes the performance hit when Disposed is used correctly (as you should always be carefull to do with objects implementing IDisposable).