fixed #484

src/Shared/HandyControl_Shared/Tools/Interop/InteropMethods.cs

@@ -91,6 +91,9 @@ namespace HandyControl.Tools.Interop
         [DllImport(InteropValues.ExternDll.User32)]
         internal static extern IntPtr GetSystemMenu(IntPtr hWnd, bool bRevert);
 
+        [DllImport(InteropValues.ExternDll.User32)]
+        internal static extern bool EnableMenuItem(IntPtr hMenu, int UIDEnabledItem, int uEnable);
+
         [DllImport(InteropValues.ExternDll.User32)]
         internal static extern bool InsertMenu(IntPtr hMenu, int wPosition, int wFlags, int wIDNewItem, string lpNewItem);
 

src/Shared/HandyControl_Shared/Tools/Interop/InteropValues.cs

@@ -73,7 +73,9 @@ namespace HandyControl.Tools.Interop
             WM_CLIPBOARDUPDATE = 0x031D,
             WM_USER = 0x0400,
             WS_VISIBLE = 0x10000000,
+            MF_BYCOMMAND = 0x00000000,
             MF_BYPOSITION = 0x400,
+            MF_GRAYED = 0x00000001,
             MF_SEPARATOR = 0x800,
             TB_GETBUTTON = WM_USER + 23,
             TB_BUTTONCOUNT = WM_USER + 24,
@@ -82,6 +84,7 @@ namespace HandyControl.Tools.Interop
             DESKTOPVERTRES = 117,
             LOGPIXELSX = 88,
             LOGPIXELSY = 90,
+            SC_CLOSE = 0xF060,
             SC_SIZE = 0xF000,
             SC_MOVE = 0xF010,
             SC_MINIMIZE = 0xF020,