C# WPF transparent window with a border

Question

I would like to make a simple application which is transparent but retains the \'normal\' borders, close button, minimize and maximize button.

I know how to make the win

Answer 1

I would first look at the (a)lpha setting in the rgb(a) color of the background color. The alpha setting sets the opacity of the object color.

Although, I notice that as I'm posting this, there is another post before mine that looks more concise and would probably be more appropriate for you.

Answer 2

I threw together a quick TransparencyConverter class based on this tutorial on Microsoft.com you can use for this purpose:

using System;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;

namespace WpfApplication2
{
    class TransparencyConverter
    {
        private readonly Window _window;

        public TransparencyConverter(Window window)
        {
            _window = window;
        }

        public void MakeTransparent()
        {
            var mainWindowPtr = new WindowInteropHelper(_window).Handle;
            var mainWindowSrc = HwndSource.FromHwnd(mainWindowPtr);
            if (mainWindowSrc != null)
                if (mainWindowSrc.CompositionTarget != null)
                    mainWindowSrc.CompositionTarget.BackgroundColor = System.Windows.Media.Color.FromArgb(0, 0, 0, 0);

            var margins = new Margins
            {
                cxLeftWidth = 0,
                cxRightWidth = Convert.ToInt32(_window.Width) * Convert.ToInt32(_window.Width),
                cyTopHeight = 0,
                cyBottomHeight = Convert.ToInt32(_window.Height) * Convert.ToInt32(_window.Height)
            };

            if (mainWindowSrc != null) DwmExtendFrameIntoClientArea(mainWindowSrc.Handle, ref margins);
        }

        [StructLayout(LayoutKind.Sequential)]
        public struct Margins
        {
            public int cxLeftWidth;
            public int cxRightWidth;
            public int cyTopHeight;
            public int cyBottomHeight;
        }

        [DllImport("DwmApi.dll")]
        public static extern int DwmExtendFrameIntoClientArea(IntPtr hwnd, ref Margins pMarInset);
    }
}

Once you have this in, add the Transparent Background attribute to your XAML and subscribe to the Window_Loaded event and call the MakeTransparent method:

<Window etc etc Background="Transparent" Loaded="Window_Loaded">

private void Window_Loaded(object sender, RoutedEventArgs e)
{
    var transparencyConverter = new TransparencyConverter(this);
    transparencyConverter.MakeTransparent();
}

A screenshot is below: