private void SetWindowTransparence() { var windowHelper = new WindowInteropHelper(AssociatedObject); var accent = new NonClientRegionAPI.AccentPolicy(); var accentStructSize = Marshal.SizeOf(accent); accent.AccentState = NonClientRegionAPI.AccentState.ACCENT_ENABLE_BLURBEHIND; var accentPtr = Marshal.AllocHGlobal(accentStructSize); Marshal.StructureToPtr(accent, accentPtr, false); var data = new NonClientRegionAPI.WindowCompositionAttributeData(); data.Attribute = NonClientRegionAPI.WindowCompositionAttribute.WCA_ACCENT_POLICY; data.SizeOfData = accentStructSize; data.Data = accentPtr; NonClientRegionAPI.SetWindowCompositionAttribute(windowHelper.Handle, ref data); Marshal.FreeHGlobal(accentPtr); }