wpf application cannot be restored from taskbar

I have a WPF application that sometimes cannot be restored from the taskbar. This typically happens when application has been running for a while but is not always the active window. When this happens, application process has to be terminated from Task Manager. What does this indicate and is there anything I can do abo开发者_JAVA技巧ut this?

TIA.

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First thing to check is that the program is not simply off screen somewhere.

• Click the icon on the taskbar
• Press Alt+Space: displays the system menu
• Press M: shows the four-arrow cursor
• Press the right arrow key ->: shows the normal cursor
• Move the mouse to move the application back onto the desktop

If this works, your next problem is to figure out how it got off screen.