title: Data grid checkbox disable un-checked option for key
body: <p>I'm using <code>DataGrid</code> and I have one column with a<code>Checkbox</code>. I would like that whenever a row has the key, the checkbox will be disabled so as to the user cannot uncheck it.
  I have a property in my view model which is called <code>IsKey</code> with <code>INotifyPropertyChanged</code>. How can I do that?</p>
  
  <p>the <code>IsChecked</code> binding is that all the <code>Checkboxes</code> are checked when starting 
  the <code>DataGrid</code> and user can uncheck rows, besides keys...</p>
  
  <pre><code>&lt;DataGridTemplateColumn.CellTemplate&gt;
     &lt;DataTemplate&gt;
        &lt;CheckBox x:Name="CheckBox" 
            IsChecked="{Binding IsChecked, UpdateSourceTrigger=PropertyChanged}"/&gt;
     &lt;/DataTemplate&gt;
  &lt;/DataGridTemplateColumn.CellTemplate&gt;
  </code></pre>