Question

I’m trying to rig up a ComboBox with a Datagrid dropdown in WPF. I need the the code to be done programmatically and contained in the codebehind.

Here’s what I’ve got so far:

                        Dim cb As New ComboBox
                        Dim dg As New DataGrid

                        dg.AutoGenerateColumns = False

                        dg.ItemsSource = clnObjects 

                        Dim col_name As New DataGridTextColumn
                        col_name.Header = "Name"
                        col_name.Binding = New Binding("Name")
                        col_name.CanUserSort = False
                        col_name.CanUserResize = False

                        dg.Columns.Add(col_name)

                        Dim col_startdate As New DataGridTextColumn
                        col_startdate.Header = "Start Date"
                        col_startdate.Binding = New Binding("StartDate")
                        col_startdate.CanUserSort = False
                        col_startdate.CanUserResize = False

                        dg.Columns.Add(col_startdate)

                        cb.Items.Add(dg)

This code produces a ComboBox that contains a DataGrid with two columns and seems to look fine. Although when you click on the ComboBox and select one of the rows in the DataGrid the selection in the ComboBox doesn’t work properly. (It just shows the colum headers.)
I want the value in the first column of the selected row to appear as the ComboBox selection.

If anyone can help me with this issue it would be greatly appretiated.

Thanks,

Mike

Answer 1

It sounds like your want your ComboBox to contain items from clnObjects, but to display the DropDown using a DataGrid, not the defaultStackPanel.

Right now your ComboBox is full of DataGrid controls, not whatever object is in clnObjects. This means when you select an item, you’re selecting a DataGrid, not the DataGrid.SelectedItem

You could try changing it so the ComboBox’s display text contains ComboBox.SelectedItem.SelectedItem where the first SelectedItem is the DataGrid, however I still feel this is a bad design since you need to create a new DataGrid object per ComboBoxItem

Instead I would recommend overwritting the default ComboBox.Template to display the ComboBox items in a DataGrid instead of in the default StackPanel. The default ComboBox Template can be found here. Just copy it and replace the StackPanel with IsItemsHost="True" to a DataGrid

<Popup x:Name="Popup" ...>
    <Grid x:Name="DropDown" ...>
      <Border x:Name="DropDownBorder" ... />
      <ScrollViewer ...>
        <!-- Replace this with a DataGrid -->
        <StackPanel IsItemsHost="True"
                    KeyboardNavigation.DirectionalNavigation="Contained" />
      </ScrollViewer>
    </Grid>
  </Popup>