title: Set checked items in CheckComboBox
body: <p>I'm using the <a href="https://wpftoolkit.codeplex.com/wikipage?title=CheckComboBox" rel="nofollow noreferrer">Xceed checkable combobox</a>.
  I need to set a few items as checked items:</p>
  <pre><code>&lt;xctk:CheckComboBox x:Name=&quot;cbFileType&quot; DisplayMemberPath=&quot;Name&quot; SelectedMemberPath=&quot;IsChecked&quot;&gt;&lt;/xctk:CheckComboBox&gt;
  </code></pre>
  <p>C# code:</p>
  <pre><code>public partial class DataSelector : UserControl
      {
          public class BoolStringClass
          {
              public string Name { get; set; }
              public bool IsChecked { get; set; }
          }
          public BackupDataSelector()
          {
              InitializeComponent();            
              cbFileType.Items.Add(new BoolStringClass { Name = &quot;.jpg&quot;, IsChecked = true });
              cbFileType.Items.Add(new BoolStringClass { Name = &quot;.bmp&quot;, IsChecked = false });
          }
      }
  </code></pre>
  <p>But &quot;.jpg&quot; item is not checked:</p>
  <p><a href="https://i.stack.imgur.com/tCpqg.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/tCpqg.jpg" alt="my CheckComboBox" /></a></p>
  <p>How can I set &quot;.jpg&quot; as checked item?</p>