title: How to handle Header click event in DataGrid in the context of MVVM?
body: <p>I know how to handle Header click event in DataGrid WPF using code-behind approach:</p>
  
  <pre><code>&lt;DataGrid&gt;
      &lt;DataGrid.Resources&gt;
          &lt;Style TargetType="DataGridColumnHeader"&gt;
              &lt;EventSetter Event="Click" Handler="columnHeader_Click" /&gt;
          &lt;/Style&gt;
      &lt;/DataGrid.Resources&gt;
  &lt;/DataGrid&gt;
  </code></pre>
  
  <p>However, I would like to handle this event in the context of MVVM. I've tried to handle by <code>System.Windows.Interactivity</code>, but I cannot figure out what I should write inside of <code>EventName</code>:</p>
  
  <pre><code>&lt;DataGrid&gt;
     &lt;i:Interaction.Triggers&gt;
        &lt;i:EventTrigger EventName="What event can I use?"
     &lt;/i:Interaction.Triggers&gt;
  &lt;/DataGrid&gt;
  </code></pre>
  
  <p>I've seen events such as <code>ColumnReordered</code>, <code>ColumnReordering</code>, but it is not applicable.</p>
  
  <p>How can I handle Header click event in DataGrid WPF in the context of MVVM?</p>