WinForms Dark title bar on Windows 10

Question

I have a WinForms application which automatically adjusts to the dark/light theme on Windows 10. My problem is that the title bar of my window always stays white, regardless which theme the user selects.

Top is current, bottom is how I want it (simulated with Photoshop)

See explorer for example. That is not an UWP app, however it uses a dark title bar on Windows 1903 and newer (when a dark theme is selected).

How can I achieve the same thing? I do not want to use any custom titlebar as I want the application to look and behave like any native application on older Windows versions as well.

Answer 1

So after some long searching, I have finally found the answer for this. The trick is to use dwmapi.dll 's DwmSetWindowAttribute and passing the undocumented constant DWMWA_USE_IMMERSIVE_DARK_MODE into the function. In C#, the code for this looks a little something like this (works with both WinForms and WPF):

/*
using System.Runtime.InteropServices;
*/

[DllImport("dwmapi.dll")]
private static extern int DwmSetWindowAttribute(IntPtr hwnd, int attr, ref int attrValue, int attrSize);

private const int DWMWA_USE_IMMERSIVE_DARK_MODE_BEFORE_20H1 = 19;
private const int DWMWA_USE_IMMERSIVE_DARK_MODE = 20;

private static bool UseImmersiveDarkMode(IntPtr handle, bool enabled)
{
    if (IsWindows10OrGreater(17763))
    {
        var attribute = DWMWA_USE_IMMERSIVE_DARK_MODE_BEFORE_20H1;
        if (IsWindows10OrGreater(18985))
        {
            attribute = DWMWA_USE_IMMERSIVE_DARK_MODE;
        }

        int useImmersiveDarkMode = enabled ? 1 : 0;
        return DwmSetWindowAttribute(handle, (int)attribute, ref useImmersiveDarkMode, sizeof(int)) == 0;
    }

    return false;
}

private static bool IsWindows10OrGreater(int build = -1)
{
    return Environment.OSVersion.Version.Major >= 10 && Environment.OSVersion.Version.Build >= build;
}

Answer 2

The fastest way:

[DllImport("DwmApi")] //System.Runtime.InteropServices
private static extern int DwmSetWindowAttribute(IntPtr hwnd, int attr, int[] attrValue, int attrSize);

protected override void OnHandleCreated(EventArgs e)
{
    if (DwmSetWindowAttribute(Handle, 19, new[] { 1 }, 4) != 0)
        DwmSetWindowAttribute(Handle, 20, new[] { 1 }, 4);
}

Answer 3

For the solution from Jonas Kohl, remember that for .net fw 4.8.1 and prior, the version returned is not ok, fixed in.Net6, here a snippet (.Net 5 is not managed):

    private static bool IsWindows10OrGreater(int build = -1)
    {
        return WindowsVersion() >= 10 && WindowsBuildNumber() >= build;
    }

    public static int WindowsVersion()
    {
     //for .Net4.8 and Minor
     #if NETFRAMEWORK
        int result = 10;
        var reg = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\Windows NT\CurrentVersion");
        string[] productName = reg.GetValue("ProductName").ToString().Split((char)32);
        int.TryParse(productName[1], out result);
        return result;
     #else
        //fixed in .Net6
        return System.Environment.OSVersion.Version.Major;
     #endif
    }

    public static int WindowsBuildNumber()
    {
        //for .Net4.8 and Minor
    #if NETFRAMEWORK
        int result = 22000;
        var reg = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\Windows NT\CurrentVersion");
        string buildNumber = reg.GetValue("CurrentBuildNumber").ToString();
        int.TryParse(buildNumber, out result);
        return result;
    #endif

    #if NET
        //fixed in .Net6
        return System.Environment.OSVersion.Version.Build;
    #endif
    }