如何通过代码打开窗口的系统菜单？

I have a C# WinForms borderless window, for which I override WndProc and handle the WM_NCHITTEST message. For an area of that form, my hit test function returns HTSYSMENU. Double-clicking that area successfully closes the form, but right-clicking it does not show the window's system menu, nor does it show up when right-clicking the window's name in the taskbar.I have a C# WinForms borderless window, for whi