Devexpress ComboBoxEditSettings not binding to ViewModel in WPF
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I'm having a problem with the DevExpress wpf grid binding when using the ComboBoxEditSettings.  Below is the grid.  I'm binding the "Associated Well Types" column to a property on my ViewModel. However, when I select some items from the combo box and then click "Ok", I see the selected items in the cell, but they don't bind back to my ViewModel.  So, do I need to do something with the "Ok" button's click event?  Is there
something in the binding that I'm not setting up properly?  All of the above? 
Thanks in advance for your help.

    <ctrls:GridControl Grid.Row="2" Grid.ColumnSpan="2" HorizontalAlignment="Stretch" Margin="5" 
                                   dx:ThemeManager.ThemeName="Office2007Blue"
                                   x:Name="gridControlForms" VerticalAlignment="Stretch"
                                   ShowLoadingPanel="{Binding TaxFormsIsBusy}"
                                   ItemsSource="{Binding TaxFormList}" >
    <ctrls:GridControl.Columns>
                <dxg:GridColumn FieldName="DisplayName" Header="Form Name" VisibleIndex="1" AllowMoving="False" />
                <dxg:GridColumn ReadOnly="True" FieldName="PrintSequence" Header="Print Sequence" VisibleIndex="2" AllowMoving="False" />
                <dxg:GridColumn Header="Associated Well Types" FieldName="SelectedWellTypes" VisibleIndex="3" AllowMoving="False" AllowBestFit="True" Width="300" >
                    <dxg:GridColumn.EditSettings>
                                <dxe:ComboBoxEditSettings ItemsSource="{Binding WellTypes}" DisplayMember="WellType" ValueMember="RenditionStateFormWellTypeId" IsTextEditable="False" >
                                    <dxe:ComboBoxEditSettings.StyleSettings>
                                                <dxe:CheckedComboBoxStyleSettings />
                                    </dxe:ComboBoxEditSettings.StyleSettings>
                                </dxe:ComboBoxEditSettings>
                    </dxg:GridColumn.EditSettings>
                </dxg:GridColumn>
    </ctrls:GridControl.Columns>           
    <ctrls:GridControl.View>
                <dxg:TableView ShowGroupPanel="False"  BestFitArea="All" AllowSorting="False" 
                                       FocusedRow="{Binding SelectedTaxForm, Mode=TwoWay}" AllowColumnFiltering="False" />
    </ctrls:GridControl.View>

</ctrls:GridControl>
