C#/WPF: Binding Combobox ItemSource in Datagrid to element outside of the DataContext

Question

I'd like to do following:

public List<Users> PreLoadedUserList { get; set; }
public List<RowEntries> SomeDataRowList { get; set; }

public class Users
{
    public int Age { get; set; }
    public string Name { get; set; }
}
public class SomeDataRowList 
{
    public int UserAge { get; set;
}

Now my (WPF Toolkit) DataGrid looks like this:

<my:DataGrid AutoGenerateColumns="False" MinHeight="200" 
             ItemsSource="{Binding Path=SomeDataRowList}">
    <my:DataGridComboBoxColumn Header="Age" 
                               ItemsSource="{Binding Path=PreLoadedUserList}" 
                               DisplayMemberPath="Name" 
                               SelectedValueBinding="{Binding Path=UserAge}"/>

</my:DataGrid>

Now my problem is, that PreLoadedUserList is outside of the ItemSource (SomeDataRowList) and I don't know how to bind to something outside of it. What I actually want it: - Display in the ComboBox PreLoadedUserList - Set the Value of (RowEntries) SelectedItem.UserAge to the Value of the selected ComboboxItem.Age

Let me know if my explanation is too weird :-)

Thank you, Cheers

Answer 1

Here we go :-)

<my:DataGridTemplateColumn Header="SomeHeader">
    <my:DataGridTemplateColumn.CellTemplate>
        <DataTemplate>
            <ComboBox SelectedValuePath="UserAge" 
                SelectedValue="{Binding Age}" 
                DisplayMemberPath="Name" 
                ItemsSource="{Binding Path=DataContext.PreLoadedUserList, 
                    RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}" 
                IsReadOnly="True" Background="White" />
        </DataTemplate>
    </my:DataGridTemplateColumn.CellTemplate>
</my:DataGridTemplateColumn>

Hope this can help someone else too.

Cheers