从父母绑定ViewModel

Question

I have a view that has a listbox in it. I have the listbox bound to a collection of ListBoxViewModel which is a property of MainViewModel. I then have a dataTemplate for the listbox in which im binding to the properties of the ListBoxViewModel. The view that contains the listbox has datacontext set to the mainVeiwModel. How can I bind to properties of the MainViewModel in the dataTemplate of the listbox that has its ItemSource bound to the collection of ListBoxVIewModels?

This combobox is in the listBox datatemplate which has its itemsoucrce bound to the collection of ListBoxViewModels. Notice im trying to bind to MainViewModel properties as well as ListBoxViewModel properties with in the datatemplate

      <ListBox ItemSource="{Binding Path=CollectionOfListBoxViewModelsInMainViewModel}"
           <DataTemplate>
               .....
                <ComboBox Margin="6"
                          Width="300"
                          IsEditable="True"
                          ItemsSource="{Binding Path=MainViewModelProperty}" //binding not working
                          SelectedItem="{Binding ListBoxViewModelProperty}"  //binding works
                          Text="{Binding ListBoxViewModelProperty, UpdateSourceTrigger=LostFocus}"/>   //binding works
                .....
          </DataTemplate>
       </ListBox>

Answer 1

Simplest way:

<YOURWINDOW x:Name="MyWindow">
 <ListBox ItemSource="{Binding Path=CollectionOfListBoxViewModelsInMainViewModel}"
           <DataTemplate>
               .....
                <ComboBox Margin="6"
                          Width="300"
                          IsEditable="True"
                          ItemsSource="{Binding ElementName=MyWindow, Path=DataContext.MainViewModelProperty}"
                          SelectedItem="{Binding ListBoxViewModelProperty}"  //binding works
                          Text="{Binding ListBoxViewModelProperty, UpdateSourceTrigger=LostFocus}"/>   //binding works
                .....
          </DataTemplate>
       </ListBox>
</YOURWINDOW>

1) Remember that MyWindow must have set DataContext to MainViewModel. You can use any UI element, it doesn't have to be Window. 2) Second solution is to use RelativeSource instead of ElementName.