WPF doesn’t have a built-in property to hide the title bar’s Close button, but you can do it with a few lines of P/Invoke.
First, add these declarations to your Window class:
private const int GWL_STYLE = -16;
private const int WS_SYSMENU = 0x80000;
[DllImport("user32.dll", SetLastError = true)]
private static extern int GetWindowLong(IntPtr hWnd, int nIndex);
[DllImport("user32.dll")]
private static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);
Then put this code in the Window’s Loaded
event:
var hwnd = new WindowInteropHelper(this).Handle;
SetWindowLong(hwnd, GWL_STYLE, GetWindowLong(hwnd, GWL_STYLE) & ~WS_SYSMENU);
And there you go: no more Close button. You also won’t have a window icon on the left side of the title bar, which means no system menu, even when you right-click the title bar – they all go together.
Important note: all this does is hide the button. The user can still close the window! If the user presses Alt+F4, or closes the app via the taskbar, the window will still close.
If you don’t want to allow the window to close before the background thread is done, then you could also override OnClosing
and set Cancel
to true, as Gabe suggested.