C# Signature:

[DllImport("user32.dll")]

static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam,IntPtr lParam);

VB Signature:

Declare Function SendMessage Lib "user32.dll" (ByVal hWnd As IntPtr, ByVal Msg As Integer,
   ByVal wParam As IntPtr, ByVal lParam As IntPtr) As IntPtr

User-Defined Types:

None.

Notes:

Parameters

hWnd can be set using the Handle property of a Control. Msg constants can be found at http://www.codeproject.com/csharp/cswindowsmessages.asp.

Tips & Tricks:

Example useage to enumerate windows, and send a message to one (in C#): http://www.sloppycode.net/sloppycode/Article-104.html

Sample Code:

C#
[DllImport("user32.dll")]
private static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam,IntPtr lParam);
private const int WM_NCPAINT = 0x0085;

// Tell ourselves to paint our border, override the WndProc method to then
// intercept this message.
private void foo()
{
    SendMessage(this.Handle,WM_NCPAINT,new IntPtr(0),new IntPtr(0));
}

Alternative Managed API:

Do you know one? Please contribute it!

(http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/windowing/messagesandmessagequeues/messagesandmessagequeuesreference/messagesandmessagequeuesfunctions/sendmessage.asp)

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