C# – Windows 7 Taskbar progress

I just wanted to add some taskbar progress animation to my WinForms application, without having to download code packs or switch to WPF to use TaskbarItemInfo.

The solution was a class that uses the ITaskbarList3 interface:

using System;
using System.Runtime.InteropServices;

public static class TaskbarProgress
{
    public enum TaskbarStates
    {
        NoProgress    = 0,
        Indeterminate = 0x1,
        Normal        = 0x2,
        Error         = 0x4,
        Paused        = 0x8
    }

    [ComImport()]
    [Guid("ea1afb91-9e28-4b86-90e9-9e9f8a5eefaf")]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    private interface ITaskbarList3
    {
        // ITaskbarList
        [PreserveSig]
        void HrInit();
        [PreserveSig]
        void AddTab(IntPtr hwnd);
        [PreserveSig]
        void DeleteTab(IntPtr hwnd);
        [PreserveSig]
        void ActivateTab(IntPtr hwnd);
        [PreserveSig]
        void SetActiveAlt(IntPtr hwnd);

        // ITaskbarList2
        [PreserveSig]
        void MarkFullscreenWindow(IntPtr hwnd, [MarshalAs(UnmanagedType.Bool)] bool fFullscreen);

        // ITaskbarList3
        [PreserveSig]
        void SetProgressValue(IntPtr hwnd, UInt64 ullCompleted, UInt64 ullTotal);
        [PreserveSig]
        void SetProgressState(IntPtr hwnd, TaskbarStates state);
    }

    [ComImport()]    
    [Guid("56fdf344-fd6d-11d0-958a-006097c9a090")]
    [ClassInterface(ClassInterfaceType.None)]
    private class TaskbarInstance
    {
    }

    private static ITaskbarList3 taskbarInstance = (ITaskbarList3)new TaskbarInstance();
    private static bool taskbarSupported = Environment.OSVersion.Version >= new Version(6, 1);

    public static void SetState(IntPtr windowHandle, TaskbarStates taskbarState)
    {
        if (taskbarSupported) taskbarInstance.SetProgressState(windowHandle, taskbarState);
    }

    public static void SetValue(IntPtr windowHandle, double progressValue, double progressMax)
    {
        if (taskbarSupported) taskbarInstance.SetProgressValue(windowHandle, (ulong)progressValue, (ulong)progressMax);
    }
}

Example of how easy it is to use:

TaskbarProgress.SetState(this.Handle, TaskbarProgress.TaskbarStates.Indeterminate);

or

TaskbarProgress.SetValue(this.Handle, 50, 100);
TaskbarProgress.SetState(this.Handle, TaskbarProgress.TaskbarStates.Error);

right click task bar. select properties. The option you are looking for is labeled taskbar buttons (see picture) and has a drop down box to the right of it. The options are:
always combine, hide labels
combine when taskbar is full
never combine