title: Draw line and move it programmatically
body: <p>I want to draw a line on a WPF Grid.</p>
  
  <pre><code>private void InitializeTestline()
  {
      testline = new Line();
      grid.Children.Add(testline);
      testline.X1 = 0;
      testline.X2 = 1;
      testline.Y1 = 0;
      testline.Y2 = 1;
      testline.HorizontalAlignment = System.Windows.HorizontalAlignment.Left;
      testline.VerticalAlignment = System.Windows.VerticalAlignment.Top;
      testline.Stroke = Brushes.Red;
      testline.Stretch = Stretch.Fill;
      testline.StrokeThickness = 2;
      testline.Visibility = System.Windows.Visibility.Visible;
  }
  </code></pre>
  
  <p>It is drawn without problems. But now i want to add four buttons to the grid (up, down, left, right). So when i press one of the buttons the line should move in the direction i choose. </p>
  
  <pre><code>private void MoveUp_Click(object sender, RoutedEventArgs e)
  {
      this.testline.Y1 += move;
      this.testline.Y2 += move;
  }
  </code></pre>
  
  <p>This was the function i want to use for this, but it doesn't work. So how it is possible to move this line?</p>
  
  <p>In end I have a gui like an old terminal3270 and these gui has a caret. the lines should be like a crosshair (and help to see where the caret actually is)</p>