What are finalisers for?

Question

I have been programming in .NET for four years (mostly C#) and I use IDiposable extensively, but I am yet to find a need for a finaliser. What are finalisers for?

Answer 1

Finalizers are only for freeing unmanaged resources like GDI bitmap handles for example. If you don't allocate any unmanaged resources then you don't need finalizers. In general it's a bad idea to touch any managed object in a finalizer because the order of finalization is not guaranteed.

One other useful technique using a finalizer is to assert that Dispose has been called when the application is required to do so. This can help catch coding errors in a DEBUG build:

void Dispose()
{
  GC.SuppressFinalize(this);
}
#if DEBUG
~MyClass()
{
  Debug.Fail("Dispose was not called.");
}
#endif