How to make a window always stay on top in .Net?


I have a C# winforms app that runs a macro in another program. The other program will continually pop up windows and generally make things look, for lack of a better word, crazy. I want to implement a cancel button that will stop the process from running, but I cannot seem to get the window to stay on top. How do I do this in C#?

Edit: I have tried TopMost=true; , but the other program keeps popping up its own windows over top. Is there a way to send my window to the top every n milliseconds?

Edit: The way I solved this was by adding a system tray icon that will cancel the process by double-clicking on it. The system tray icon does no get covered up. Thank you to all who responded. I read the article on why there is not a 'super-on-top' window... it logically does not work.

3/26/2009 3:05:11 PM

Accepted Answer

Form.TopMost will work unless the other program is creating topmost windows.

There is no way to create a window that is not covered by new topmost windows of another process. Raymond Chen explained why.

3/18/2019 4:35:58 PM

I was searching to make my WinForms application "Always on Top" but setting "TopMost" did not do anything for me. I knew it was possible because WinAmp does this (along with a host of other applications).

What I did was make a call to "user32.dll." I had no qualms about doing so and it works great. It's an option, anyway.

First, import the following namespace:

using System.Runtime.InteropServices;

Add a few variables to your class declaration:

private static readonly IntPtr HWND_TOPMOST = new IntPtr(-1);
private const UInt32 SWP_NOSIZE = 0x0001;
private const UInt32 SWP_NOMOVE = 0x0002;

Add prototype for user32.dll function:

[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X, int Y, int cx, int cy, uint uFlags);

Then in your code (I added the call in Form_Load()), add the call:

SetWindowPos(this.Handle, HWND_TOPMOST, 0, 0, 0, 0, TOPMOST_FLAGS);

Hope that helps. Reference

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