CODE EXAMPLE FOR CSHARP

add buttons to taskbar thumbnail WPF

<Window.TaskbarItemInfo>
    <TaskbarItemInfo>
        <TaskbarItemInfo.ThumbButtonInfos>
            <ThumbButtonInfo ImageSource="/IconProgressDemo;component/Icon1.ico" Description="Play!" Click="ThumbButtonInfo_Click" />
            <ThumbButtonInfo ImageSource="/IconProgressDemo;component/Icon2.ico" Description="Stop!" Click="ThumbButtonInfo_Click" />
        </TaskbarItemInfo.ThumbButtonInfos>
    </TaskbarItemInfo>
</Window.TaskbarItemInfo>