MyControl.xaml

<UserControl x:Class="Utkarsh.HierarchyDemo.MyControl"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             Background="{DynamicResource VsBrush.Window}"
             Foreground="{DynamicResource VsBrush.WindowText}"
             mc:Ignorable="d"
             d:DesignHeight="300" d:DesignWidth="300"
             Name="MyToolWindow">
    <Grid>
        <StackPanel Orientation="Vertical">
            <TextBlock Margin="10" HorizontalAlignment="Center">My Tool Window</TextBlock>
            <Button Content="_Click Me!" Click="button1_Click" Width="120" Height="80" Name="button1"/>
        </StackPanel>
    </Grid>
</UserControl>