How to Create a WPF User Control & Use It in a WPF Application ( C# )

<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:myToolTip="clr-namespace:CustomToolTip;assembly=CustomToolTip"
    Title="Window1" Height="600" Width="800">
    <Grid x:Name="rootGrid" RenderTransformOrigin="0.5,0.5">
    	<Grid.RenderTransform>
    		<TransformGroup>
    			<ScaleTransform ScaleX="1" ScaleY="1"/>
    			<SkewTransform AngleX="0" AngleY="0"/>
    			<RotateTransform Angle="0"/>
    			<TranslateTransform x:Name="rootGridXY" X="0" Y="0"/>
    		</TransformGroup>
    	</Grid.RenderTransform>
        <Rectangle Margin="26,34,496,374" Name="rectangle1" Stroke="Black" 
                   Fill="Coral" MouseLeave="rectangle_MouseLeave" MouseMove="rectangle_MouseMove" />
        <Rectangle Fill="Lavender" Margin="537,29,53,376" Name="rectangle2" 
                   Stroke="Black" MouseMove="rectangle_MouseMove" MouseLeave="rectangle_MouseLeave" />
        <Rectangle Fill="Peru" Margin="192,391,186,37.995" Name="rectangle3" 
                   Stroke="Black" MouseMove="rectangle_MouseMove" MouseLeave="rectangle_MouseLeave" />
        <myToolTip:UserControl1 UserControlTextBlockToolTip="Some texts" 
                                UserControlToolTipTitle="Title" 
                                Visibility="Hidden" 
                                x:Name="customToolTip" />
    </Grid>
</Window>