Step 1 : Write the below code with in MainWindow.xaml


<Window x:Class="Drawline.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Line X1="10" Y1="10" X2="250" Y1="250" Stroke="Green" StrokeThickness="4" Margin="0,0,1,23"/> 
   </Grid>
</Window>

Output :


wpf18