C＃总是像TopMost一样设置一个窗体，但是与其他窗口的交互总是可能的

Question

This is a screenshot of a Form . It's basically just those two lines at the top of a screen, when you hover them this little window pops up. I just wonder what these two lines might be.

I did not find any information on the internet on how to achieve something familiar. I just want to know what idea is behind that, maybe some sample code would be nice to illustrate this idea.

Is this just some sort of custom window ? Is WPF probably the way to go then? If so, how is it possible to set a Form always visible and usable (it is not required to click on the Form to get the focus to be able to interact with it) even though it can't be set as TopMost Form ?

this.TopMost = true;

Because I can still interact with other windows, while the two lines custom form is still visible and overlaying all other windows. But under no circumstance this two lines custom form gets overlayed. What idea is behind this custom Form ?

---

Update:

After some additional research on the internet, it seems like the TopMost property doens't behave as you expect sometimes. I just tested it a few more times and now it is behaving exactly the way I described I want it to be.

---

Update on how this two lines Form work:

Imagine you have any window open in FullScreen. But the two lines Form is at the top of your screen. It hovers all other windows, but doesn't declare it's own space like an AppBar . The two lines Form gets never hidden, so there is no AutoHide involved. It's just the window with " Screenshot region ", ...that pops up once the two lines Form get's hovered. Furthermore the two lines Form is bound to the top of the screen.

Answer 1

It should work just fine with TopMost = true (in WinForms and in WPF too). TopMost means window will be always displayed over any other windows without this flag set (so another topmost window might overlay your topmost window), including currently active window. So most likely what is on your screenshot is just topmost window with very small size aligned to the top of screen, which shows another window (or expands itself) on mouse over and hides that window (or shrinks itself) when mouse is out. I'm not an expert on WinForms, so if that doesn't work in some cases for you - you might find some information in google about why and when it doesn't work (for example some people claim it doesn't work when you run application from Visual Studio, so ensure you run it standalone while testing). But in general TopMost property should do just what you describe.