Processing custom windows message

[Ryan Fransen]

I have created a custom windows message and using SendNotifyMessage
(user32.dll) the message is sent (broadcasted).

I send the message as follows:
[DllImport("user32.dll", CharSet=CharSet.Auto)]
private static extern int SendNotifyMessage(IntPtr hwnd, IntPtr
wMsg,
IntPtr wParam,
IntPtr lParam);

SendNotifyMessage((IntPtr)0xffff, RegisterWindowMessage("somestring"),
Marshal.StringToHGlobalAuto("a message"),
Marshal.StringToHGlobalAuto("another message"));

I am receiving the message in another c# app as follows:

protected override void
WndProc(ref System.Windows.Forms.Message m)
{
if(m.Msg == RegisterWindowMessage("somestring"))
{

string s = Marshal.PtrToStringAuto(m.WParam);
}

else
{
base.WndProc(ref m);
}
}
The message is received in WndProc without any problems, however the
lparam and wparam properties (when marshalled) have empty strings.

It seems that the pointer created in the sendmessage call points to a
section in memory that when in the WndProc call points to nothing at
all.

When I inspect the memory location in the app that sends the message,
the messages are in fact there.

Does anyone have any advice or suggestions as to what might be wrong?

Thanks in advance.

Ryan Fransen

[Mattias Sjögren]

Ryan,

SendNotifyMessage((IntPtr)0xffff, RegisterWindowMessage("somestring"),
Marshal.StringToHGlobalAuto("a message"),
Marshal.StringToHGlobalAuto("another message"));
You're leaking memory here by not freeing the memory you allocate.

Does anyone have any advice or suggestions as to what might be wrong?

The pointers are only valid in the process that sends the message. If
you want to transfer strings to other applications you should look at
using WM_COPYDATA or shared memory.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Ryan Fransen]

Mattias Sjögren <ma********************@mvps.org> wrote in message news:<u$*************@TK2MSFTNGP15.phx.gbl>...

Ryan,

SendNotifyMessage((IntPtr)0xffff, RegisterWindowMessage("somestring"),
Marshal.StringToHGlobalAuto("a message"),
Marshal.StringToHGlobalAuto("another message"));

You're leaking memory here by not freeing the memory you allocate.

Does anyone have any advice or suggestions as to what might be wrong?

The pointers are only valid in the process that sends the message. If
you want to transfer strings to other applications you should look at
using WM_COPYDATA or shared memory.

Mattias

Once again, Mattias saves the day...

Thanks again for your help.

Ryan