Bind ComboBox in DataGrid to collection in view

Question

I have a view that is bound to my usercontrol. On my usercontrol I have a datagrid which is bound to a collection from my view. One column in that datagrid is a DataGridComboBoxColumn and I need to bind it to a different collection in my view. The binding of the datagrid looks like this:

DataContext="{Binding .}" ItemsSource="{Binding VictimVillages}"

The datacontext is the view and VictimVillages is the collection I want to display in the datagrid.

I have tried to access the collection I want to display in the combobox with

ItemsSource="{Binding Path=Patterns,RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type Views:ViewPlanner}}}"

The name of the collection is Patterns, the type of the view is "ViewPlanner", which is in the Views namespace.

I have create a diagram of the dependencies. I need help to figure out the yellow part.

Answer 1

when using RelativeSource Binding you(mostly) have to use DataContext.YourProperty in your Binding Path.

if your datacontext from the DataGrid also have the Patterns Collection you can do this

ItemsSource="{Binding Path=DataContext.Patterns,RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type DataGrid}}}"

i often use "MarkerInterface" for Relative bindings. that mean empty interfaces that i can add to my views.

public interface IDataContextMarker4PatternCollection {}

now add this interface to your view/usercontrol where the Pattern Collection Property is in the Datacontext.

and now you can simply use RelativeSourceBinding

 ItemsSource="{Binding Path=DataContext.Patterns,RelativeSource={RelativeSource AncestorType={x:Type local:IDataContextMarker4PatternCollection }}}"