Undefined local handles

[Alison Kakoschke]

I need to get a device context for a form. I'm doing
this by using Graphics.getHdc();
This returns what appears to be a valid IntPtr, however
when I convert this to a HDC by using either
HDC hdc = (HDC) (void*) myIntPtr; or
HDC hdc = (HDC) myIntPtr.ToInt32();
I get an undefined value for hdc.

That is, when I place a watch on the variable I get the
following
{HDC__} { unused=<undefined value> }
as its value.
Note that when I define the HDC as a member variable of a
class, I get a valid value. When it is defined local to
a method, I get the above undefined value.