Question

There’s a great code sample in this post:

DateTimePicker automatically move to next datepart

which shows how to clean up some of the behavior of the DateTimePicker in .NET. Unfortunately the code won’t compile, since .NET can’t understand the WM_KEYDOWN type stuff. I was able to google and get values for a lot of the constants, like

WM_KEYUP = 0x0101;

But I’m really stuck getting NMHDR and WM_REFLECT to work. Is there some sort of Win32 assembly I need to add to my project to get all of this to work?

Thanks!

Answer 1

You need to use what is known as P/Invoke.

[…] As an increasing developer base moves
its production applications to managed
code, it seems only natural that there
will be even more occasions for
developers to dip down into the
underlying operating system for some
critical tidbit of functionality—at
least for the time being. Thankfully,
the interop features of the common
language run-time (CLR), called
Platform Invoke (P/Invoke), are very
complete […].

http://www.pinvoke.net/default.aspx/Constants/WM.html

private const UInt32 WM_KEYDOWN        = 0x0100;

http://www.pinvoke.net/default.aspx/Structures/NMHDR.html

[StructLayout(LayoutKind.Sequential)] 
struct NMHDR 
{
   public IntPtr hwndFrom;
   public IntPtr idFrom;
   public int code;
}