title: Update and refresh wpf chart
body: <p>I'm working with chart of wpf toolkit, and I can't view the inserted data of the chart... Here is the xaml part:</p>
  
  <pre><code>&lt;chartingToolkit:Chart  Height="352" HorizontalAlignment="Left" Name="profilo_cale_chart" Title="Profili cale" VerticalAlignment="Bottom" Width="655" FontSize="16" Margin="252,0,0,55" Visibility="Hidden"&gt; 
     &lt;chartingToolkit:AreaSeries DependentValuePath="Value" IndependentValuePath="Key" IsSelectionEnabled="True" ItemsSource="{Binding}" Foreground="#FF242424" Background="LightSteelBlue" /&gt;
  &lt;/chartingToolkit:Chart&gt;
  </code></pre>
  
  <p>And the cs:
  Declaration </p>
  
  <pre><code>public partial class MainWindow : Window
  { ...  
      List&lt;KeyValuePair&lt;DateTime, double&gt;&gt; valueList = new List&lt;KeyValuePair&lt;DateTime, double&gt;&gt;(); 
  ...
  </code></pre>
  
  <p>Module called when a user chose two dateTime and press a button</p>
  
  <pre><code>private void refresh_charts(DateTime dtStart, DateTime dtEnd)
  {
      valueList.Clear();
      using (ModelFoosContainer mc1 = new ModelFoosContainer())
      {
          var res_mea = (from mea in mc1.MeasureSet where (mea.datetime&gt;= dtStart &amp;&amp; mea.datetime &lt;= dtEnd) orderby mea.datetime descending select mea).Take(1000);
          foreach (Measure mea1 in res_mea){
              valueList.Add(new KeyValuePair&lt;DateTime,double&gt;(mea1.datetime, Convert.ToDouble(mea1.depth)));
          }
      }
  
  
      profilo_cale_chart.DataContext = valueList;
      //I've tried with this two but doesn't work..
      //profilo_cale_chart.Refresh();
      //this.UpdateLayout();
  
  }
  </code></pre>
  
  <p>After this the chart has the right and not empty DataContext but doesn't show the values... anyone knows how can I fix it? </p>