title: OxyPlot find the selected LineSeries
body: <p>I have a <code>PlotModel</code> with multiple <code>LineSeries</code> painted. 
  What I'm looking for is a trick to select all the LineSeries which the point, detect by the <code>MouseDown</code> event, belongs to.</p>
  
  <p>I've done this:</p>
  
  <pre><code>this.MouseDown += CheckIfLineSeriesHasBeenSelected;
  
  private void CheckIfLineSeriesHasBeenSelected(object sender, OxyMouseDownEventArgs e)
  {
       switch (e.ChangedButton)
       {
            case OxyMouseButton.Left:
                 var series = (LineSeries) this.GetSeriesFromPoint(e.Position, 10);
                 series.StrokeThickness = 4;
             break;
        }
   }
  </code></pre>
  
  <p>But in this way the model changes the thickness of only a small part of the entire LineSeries.
  Do you have any suggestions? 
  Thanks!</p>