C＃WPF DataGrid：DataGridComboxBoxColumn绑定ItemsSource失败

Question

i want to display a ComboBox on my DataGrid . But the ComboBox does not load the ObservableCollection . My ObservableCollection 'Projects' is on my ViewModel defined. The problem is not the DataContext . But when I define the ComboBox outside of my DataGrid , the binding works. Does anyone have an idea where my problem is?

ViewModel:

public Project SelectedProject
{
    get { return _project; }
    set
    {
        if (_project != value)
        {
            _project = value;
            OnPropertyChanged();
            _actions = _database.LoadActions(SelectedProject.Id);
            OnPropertyChanged(() => Actions);
        }
    }
}

public ObservableCollection<Project> Projects
{
    get { return _database.LoadProjects(); }
}

XAML:

<DataGridComboBoxColumn Header="Projekt:" Width="140" DisplayMemberPath="Name">
    <DataGridComboBoxColumn.ElementStyle>
        <Style TargetType="ComboBox">
            <Setter Property="ItemsSource" Value="{Binding Projects, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}"/>
            <Setter Property="SelectedItem" Value="{Binding SelectedProject, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
        </Style>
    </DataGridComboBoxColumn.ElementStyle>
    <DataGridComboBoxColumn.EditingElementStyle>
        <Style TargetType="ComboBox">
            <Setter Property="ItemsSource" Value="{Binding Projects, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" />
            <Setter Property="SelectedItem" Value="{Binding SelectedProject, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
            <Setter Property="IsDropDownOpen" Value="True" />
        </Style>
    </DataGridComboBoxColumn.EditingElementStyle>

Answer 1

Try this:

<Setter Property="ItemsSource" Value="{Binding DataContext.Projects, RelativeSource={RelativeSource AncestorType=DataGrid}}"/>

The DataContext of the ComboBox in a DataGridComboBoxColumn is the corresponding object in the DataGrid 's ItemsSource .

If your Projects collection is defined in the view model, you need to specify a RelativeSource for the binding to work.