can't get form to remain on top, in .net

Question

I can't get a form to remain on top, in .net

I have checked How to make form always on top in Application and the answer there mentions form1.TopLevel = true; and I've checked How to make a window always stay on top in .Net? and it says Form.ActiveForm.TopMost so i've tried Form.ActiveForm.TopMost = true; and this.TopMost = true;

private void Form1_Load(object sender, EventArgs e)
{
  this.TopLevel = true; //default anyway

  Form.ActiveForm.TopMost = true;
  this.TopMost = true;  
}

But as you can see, a notepad window or any window can cover it.

Added

I have tried every suggestion made so far.

In response to Han's advice, "Of all the possible places to set TopMost property, the Load event is the worst. It should be set in the constructor, so the window gets created top-most right away. Or it should be set after it is visible, so after the Load event. Use the constructor. ". I tried putting those lines in the constructor.

    public Form1()
    {
        InitializeComponent();
        this.TopLevel = true; //default anyway

        //Form.ActiveForm.TopMost = true; (commented to prevent a System.InvalidOperationException, presumably the form isn't yet active at this stage)
        this.TopMost = true;
    }

And the the other two suggestions, from others-

I tried setting the Form's TopMost field in the designer to True.

And running the EXE directly rather than just clicking play in visual studio.

Same issue.

And if you find that hard to believe, i've taken a 1min video here showing just that. https://screencast-o-matic.com/watch/cbXXrw2oTN

A potentially useful comment was mentioned..

Steve comments - "OK something definitively odd is happening here. I have tried to create a simple topmost form using linqpad and at the first run I get your same behavior. At the second run though everything works as expected."

Answer 1

A workaround, is this, following on from Han's point to put not put it in Load. Load is indeed too early. I've been finding that (at least on the system with the issue), The Constructor is also too early. I find that putting it in the Shown event, works.

One possible solution to this, is to run this patch, https://support.microsoft.com/en-us/help/2587473/topmost-windows-are-not-always-in-the-topmost-position-in-windows-7-or But be warned, if you want to uninstall it, I have some doubts whether it uninstalls correctly. And it's also not clear to me whether the patch is working or working sporadically. It likely works but it's hard for me to tell.

One commenter thought it's just my system, though that's not the case, as Steve ran into the same issue the first time he ran it. I find it may be most prone to happen after windows restarts, So, the program is running very fresh. But I find that putting that code in the Shown event, is fine and the form stays on top.

I tried instead of TopMost=true, using SetWindowPos, to set the window on top, I tried it fairly early like in the constructor, and late, like in the Shown event or on a button click, and I found it was fine in the Shown event or on a button click. So the issue was related to the TopMost=true line, or SetWindowPos line, firing too early, prior to the window it is setting appearing.

When calling SetWindowPos later one can use either this.Handle or GetForegroundWindow(), the former is easier as it's native. When calling it earlier one must use this.Handle. And using this.TopMost=true avoids all winAPI calls completely.

So in short, you could try the patch, though note that it might not uninstall right.. Or you can try the workaround of putting this.TopMost=true in the Shown event of the form.