title: How to remove a single child of a single canvas after I added it?
body: <p>I have a WPF project where i have to create a few ellipses on a canvas. I create two check Box and when i check on the first checkbox, the red ellipse will show on the canvas. If i uncheck the first check box, the ellipse will be disappear....the second check box will have the same function by creating a blue ellipse instead. </p>
  
  <p>So heres my situation, when the two checkboxes are checked, a blue and a red ellipse will appear. To clear the ellipse on the canvas, i use the <code>myCanvas.children.clear()</code>. But when i uncheck one of the checkbox, both of the ellipse will be deleted. </p>
  
  <pre><code>private void redCB_Checked(object sender, RoutedEventArgs e)
      {
         drawRedCircle();
      }
  
  private void redCB_Unchecked(object sender, RoutedEventArgs e)
      {
         myCanvas.Children.Clear();
      }
  
  private void blueCB_Checked(object sender, RoutedEventArgs e)
      {
         drawBlueCircle();
      }
  
  private void blueCB_Unchecked(object sender, RoutedEventArgs e)
      {
         myCanvas.Children.Clear();
      }
  
  private void drawRedCircle()
      {
          Ellipse myCircle = new Ellipse();
          myCircle.Stroke = Brushes.Red;
          myCircle.Width = 30;
          myCircle.Height = 30;
          myCircle.StrokeThickness = 2;
  
          Canvas.SetLeft(myCircle, 10);
          Canvas.SetRight(myCircle, 10);
          Canvas.SetBottom(myCircle, 10);
          Canvas.SetTop(myCircle, 10);
  
          myCanvas.Children.Add(myCircle);
      }
  
   private void drawBlueCircle()
      {
          Ellipse myCircle = new Ellipse();
          myCircle.Stroke = Brushes.Blue;
          myCircle.Width = 30;
          myCircle.Height = 30;
          myCircle.StrokeThickness = 2;
  
          Canvas.SetLeft(myCircle, 20);
          Canvas.SetRight(myCircle, 20);
          Canvas.SetBottom(myCircle, 20);
          Canvas.SetTop(myCircle, 20);
  
          myCanvas.Children.Add(myCircle);
      }
  </code></pre>