Posts Tagged ‘XAML’

XAML DataGrid using one DataTable as lookup

Četrtek, Februar 26th, 2015

Problem:

I have a DataTable with lookup column into another table. Another table is a small table so all the records can fit in small combobox and the user wants to be able to select lookup record with combobox.

Solution:

XAML has DataGridComboBoxColumn, but it is difficult to bind, because DataGridComboBoxColumn can’’t bind to Windows binding source. It is obviously quite know problem, but I could’n’t find an easy solution.

Test tables:

MAIN_TABLE 
{ 
  ID, 
  SubTableID, 
  ... other fields ...
}

SUB_TABLE 
{ 
  ID, 
  Description 
}

Naive

Naive solution, that doesn’’t work

<DataGrid ItemsSource="{Binding mainTable}">
  <DataGrid.Columns>
    <DataGridTextColumn Header="ID" 
                        Binding="{Binding ID}" />
    <DataGridTextColumn Header="SubID" 
                        Binding="{Binding SubTableID }" />
    <DataGridComboBoxColumn Header="Desc" 
                            ItemsSource="{Binding subTable}}" <!-- can't bind! -->
                            SelectedValueBinding="{Binding SubTableID}"
                            SelectedValuePath="ID" 
                            DisplayMemberPath="Description" />
  </DataGrid.Columns>            
</DataGrid>

The solution doesn’’t work because – for some reason– DataGridComboBoxColumn can’’t bind subTable even if it is defined exactly as mainTable in datasource for the whole xaml window.

Solution

The solution is quite easy. Create a resource that binds to sub table and then use that resurce sa data source 🙂


<DataGrid ItemsSource="{Binding mainTable}">
  <DataGrid.Resources>
    <CollectionViewSource x:Key="cvsSubTable" 
                          Source="{Binding subTable }"/> <!-- can bind! -->
  </DataGrid.Resources>
  <DataGrid.Columns>
    <DataGridTextColumn Header="ID" 
                        Binding="{Binding ID}" />
    <DataGridTextColumn Header="SubID" 
                        Binding="{Binding SubTableID }" />
    <DataGridComboBoxColumn Header="Desc" 
                            ItemsSource="{Binding Source={StaticResource cvsSubTable }}"  <!-- now it is ok! --> 
                            SelectedValueBinding="{Binding SubTableID}"
                            SelectedValuePath="ID" 
                            DisplayMemberPath="Description" />
  </DataGrid.Columns>            
</DataGrid>         

Lost 4 hours on that! Grrrr..