The main window is the window that is created when the process is started. After initialization, other windows may be opened, including the Modal and TopLevelwindows, but the first window associated with the process remains the main window.
You can get the MainWindowHandle property only for processes that are running on the local computer. The MainWindowHandle property is a value that uniquely identifies the window that is associated with the process.
A process has a main window associated with it only if the process has a graphical interface. If the associated process does not have a main window, theMainWindowHandle value is zero. The value is also zero for processes that have been hidden, that is, processes that are not visible in the taskbar. This can be the case for processes that appear as icons in the notification area, at the far right of the taskbar.
If you have just started a process and want to use its main window handle, consider using the WaitForInputIdle method to allow the process to finish starting, ensuring that the main window handle has been created. Otherwise, an exception will be thrown.
Windows 98, Windows Millennium Edition Platform Note: This property is not available on this platform if you started the process withProcessStartInfo.UseShellExecute set to true.
process.MainWindowHandle很多情况下为0，注意红字部分。