title: Update items in ComboBox after lookup value is added
body: <p>I have a WPF form that contains a DataGrid. This DataGrid is editable. One column of the DataGrid  contains a ComboBox with a list of lookup codes for the user to select from.</p>
  
  <p>While editing, the user can add a new lookup code by calling a modal window. When control is returned to the DataGrid, the combobox does not have the new lookupcode.</p>
  
  <p>How can I refresh the list in the combobox after an item is added?</p>
  
  <p>Here is how my combobox is defined. Below is the column of the DataGrid and then my dictionary snippet.</p>
  
  <pre><code>&lt;DataGridTemplateColumn Header="Type" Width="160"&gt;
  &lt;DataGridTemplateColumn.CellTemplate&gt;
      &lt;DataTemplate&gt;
          &lt;TextBlock Text="{Binding AddrType.Description}"/&gt;
      &lt;/DataTemplate&gt;
  &lt;/DataGridTemplateColumn.CellTemplate&gt;
  &lt;DataGridTemplateColumn.CellEditingTemplate&gt;
      &lt;DataTemplate&gt;
          &lt;StackPanel Orientation="Horizontal"&gt;
              &lt;ComboBox Name="cboAddrtype" 
                        ItemsSource="{Binding Source={StaticResource addrTypeList}}" 
                        SelectedValuePath="ID" 
                        DisplayMemberPath="Description" 
                        SelectedValue="{Binding AddrTypeID, UpdateSourceTrigger=PropertyChanged}" 
                        Width="100" /&gt;
              &lt;Button ToolTip="New" Name="btnNewAddressType" Click="btnNewAddressType_Click"&gt;
                  &lt;Image Source="Images\Add.png" Style="{StaticResource buttonImageStyle}" /&gt;
              &lt;/Button&gt;
          &lt;/StackPanel&gt;
      &lt;/DataTemplate&gt;
  &lt;/DataGridTemplateColumn.CellEditingTemplate&gt;
  </code></pre>
  
  <p></p>
  
  <p>The method GetAddressTypes() returns an ObservableCollection.</p>
  
  <pre><code>&lt;ObjectDataProvider x:Key="addrTypeList" IsAsynchronous="True"
                      MethodName="GetAddressTypes"
                      ObjectType="{x:Type components:AddressComponent}"/&gt;
  </code></pre>