Finalizers with Dispose() in C#

Question

See the code sample from MSDN: ( http://msdn.microsoft.com/en-us/library/b1yfkh5e(v=VS.100).aspx )

// Design pattern for a base class.
public class Base: IDisposable
{
  private bool disposed = false;

  //Implement IDisposable.
  public void Dispose()
  {
      Dispose(true);
      GC.SuppressFinalize(this);
  }

  protected virtual void Dispose(bool disposing)
  {
      if (!disposed)
      {
          if (disposing)
          {
              // Free other state (managed objects).
          }
          // Free your own state (unmanaged objects).
          // Set large fields to null.
          disposed = true;
      }
  }

  // Use C# destructor syntax for finalization code.
  ~Base()
  {
      // Simply call Dispose(false).
      Dispose (false);
  }
}

In the Dispose() implementation it calls GC.SupressFinalize();, but provide a destructor to finalise the object.

What is the point of providing an implementation for the destructor when GC.SuppressFinalize() is called?

Just little bit confused what the intentions are?

Answer 1

If someone forgets to call Dispose, the finalizer will (eventually) run to do final cleanup. Since finalization hurts performance, ideally no-one will forget to Dispose. The using construct helps a little with that.

Answer 2

There are 2 scenarios:

• Your code calls Dispose (preferred) and the Finalizer is canceled, eliminating the overhead.
• Your code 'leaks' the object and the GC calls the Finalizer.