Question

I would like to make a two way editable datagrid with a combobox column.
This datagrid is connected to a .NET Entity Framework. How could I do this? Could you extend my code?

SQL:

CREATE TABLE Languages(
    L_Id INTEGER PRIMARY KEY IDENTITY(1,1),
    L_Name VARCHAR(16) NOT NULL
);

CREATE TABLE Movies (
    M_Id INTEGER PRIMARY KEY IDENTITY(1,1),
    M_Title VARCHAR(128) NOT NULL,
    M_Language_Id INTEGER NOT NULL,

    CONSTRAINT MoviesToLanguages 
        FOREIGN KEY (M_Language_Id) 
        REFERENCES Languages (L_Id)
);

INSERT INTO Languages VALUES('subtitled');
INSERT INTO Languages VALUES('synchronized');

MainWindow.xaml

...
<DataGrid Name="MoviesDataGrid" Grid.Row="1" AutoGenerateColumns="False" ItemsSource="{Binding Movies}">
    <DataGrid.Columns>
        <DataGridTextColumn Header="Title" Binding="{Binding M_Title}" />
        <DataGridTemplateColumn Header="Language" CanUserReorder="False">
            <DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                        <TextBlock TextAlignment="Center" Text="{Binding Path=Languages.L_Name}"/>
                </DataTemplate>
            </DataGridTemplateColumn.CellTemplate>
            <DataGridTemplateColumn.CellEditingTemplate>
                <DataTemplate>
                    ???
                </DataTemplate>
            </DataGridTemplateColumn.CellEditingTemplate> 
        </DataGridTemplateColumn>
    </DataGrid.Columns>
</DataGrid>
...

CinemaViewModel.cs

private CinemaEntities _Entities;
public ObservableCollection<Movies> Movies{ get; private set; }

public CinemaViewModel()
{
    _Entities = new CinemaEntities();
    Movies = new ObservableCollection<Movies>(_Entities.Movies.Include("Languages"));
    OnPropertyChanged("Movies");
}

private void Save()
{
    _Entities.SaveChanges();
}

Answer 1

In your DataTemplate:

<ComboBox ItemsSource="{Binding DataContext.Movies, RelativeSource={RelativeSource FindAncestor, AncestorType=DataGrid}" SelectedItem="{Binding WhateverPropertyReferencesTheMovieNavigationPropertyInYourEntities}" DisplayMemberPath="WhateverPropertyInTheMoviesYouWantToVisualizeInTheComboBox"/>