title: DataGrid.SortMemberPath doesn't work
body: <p>I created a <code>DataGrid</code> with binding to <code>DataTable</code>, here:</p>
  
  <pre><code>&lt;DataGrid1:DataGrid x:Name="dg" CanUserDeleteRows="True" AutoGenerateColumns="False" ItemsSource="{Binding MyDataTable}"&gt;
  &lt;DataGrid1:DataGrid.Columns&gt;
    &lt;DataGrid1:DataGridTemplateColumn SortMemberPath="[First Column name]" Header="First Column name"&gt;
        &lt;DataGrid1:DataGridTemplateColumn.CellTemplate&gt;
           &lt;DataTemplate&gt;
               &lt;TextBox Text="{Binding [First Column name],Mode=TwoWay}" /&gt;
           &lt;/DataTemplate&gt;
        &lt;/DataGrid1:DataGridTemplateColumn.CellTemplate&gt;
     &lt;/DataGrid1:DataGridTemplateColumn&gt;
  &lt;/DataGrid1:DataGrid.Columns&gt;
  &lt;/DataGrid1:DataGrid&gt;
  </code></pre>
  
  <p>and when I click on header to sort the table, I get this exception :</p>
  
  <blockquote>
    <p>An unhandled exception of type 'System.ArgumentException' occurred in PresentationFramework.dll</p>
    
    <p>Additional information: 'My_Table_Name' type does not have property named '[First Column name]', so cannot sort data collection.</p>
  </blockquote>