Question

I am an absolute beginner to WPF applications and need some help. All I’m trying to do is draw a rectangle from point A to point B, and be able to detect when the rectangle is clicked. So when it is clicked it turns yellow and when clicked again, red.

Answer 1

There are multiple ways to do this.

1. Add a click handler to the rectangle, and toggle its color from code behind
2. Bind the rectangle’s color to a View Model property, and set the property on click using a Delegate Command.

The first is easiest if you’re just starting with XAML (although #2 is recommended if you want to adhere to MVVM).

 <Rectangle x:Name="rect" 
    Width="100" Height="100" Fill="Aquamarine" 
    MouseLeftButtonDown="Rectangle_MouseLeftButtonDown" />

And the code-behind handler:

 bool toggle = false;

 private void Rectangle_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
 {
     rect.Fill = new SolidColorBrush(toggle ? Colors.Aquamarine : Colors.DarkRed);
     toggle = !toggle;
 }