There seem to be two basic ways of dealing with lParam values when
overriding the WndProc --

1) us Marshal.PtrToStructure/StructureToPtr
2) use an unsafe code block and do a cast

It seems like the latter is more annoying...

Suppose I want to change value of a struct member in the lParam.  By method
#1, you'd need something like the following:

protected override bool OnWindowPosChanged(ref Message m)
{
   Win32.WINDOWPOS w = Marshal.PtrToStructure(m.lParam,
typeof(Win32.WINDOWPOS));

   w.cy += 3; // we're chaging the height of the window...

   Marshal.StructureToPtr(m.lParam, w, true);

return false;
}

The key annoyance is that you have to also call the last StructureToPtr to
put the changed data back...  Now if this was in one place, then ok, but if
you're doing this all over the place, it quickly becomes annoying.

Using an unsafe block we could do something like:

protected override bool OnWindowPosChanged(ref Message m)
{
   unsafe
{
   Win32.WINDOWPOS* w = (Win32.WINDOWPOS*)m.lParam;

   w->cy += 3;
}
return false;
}

Using the unsafe block changes the original structure rather than a copy of
it.  Are these really the two only options?  Assuming that we have Full
Trust anyway (since we're doing a ton of P/Invoke already), is there a
reason not to use method #2?

Regards,
--Oren