问我需要什么来进一步限定绑定的DataContext？

EN

TechnicainSelectionView.xaml
TechnicianSelectionView.cs
TechnicianSelectionViewModel.cs
Technician.cs (Code First Entity)

<UserControl xmlns etc... here" 
             d:DesignHeight="48" d:DesignWidth="300">
    <Grid>
        <StackPanel>
            <Label Content="Select a Technican to run the test" FontWeight="Bold"></Label>
            <ComboBox ItemsSource="{Binding Technicians, Mode=TwoWay}"></ComboBox>
        </StackPanel>
    </Grid>
</UserControl>

public partial class TechnicianSelectionView : UserControl
{
    public TechnicianSelectionViewModel ViewModel { get; private set; }

    public TechnicianSelectionView()
    {
        InitializeComponent();

        Technician.GenerateSeedData();

        ViewModel = new TechnicianSelectionViewModel();
        DataContext = ViewModel;
    }
}

public class TechnicianSelectionViewModel : ViewModelBase
{
    public ObservableCollection<Technician> Technicians { get; set; }

    public TechnicianSelectionViewModel()
    {
        Technicians = new ObservableCollection<Technician>();
    }

    public bool IsLoaded { get; private set; }

    public void LoadTechnicians()
    {
        List<Technician> technicians;

        using (var db = new TestContext())
        {
            var query = from tech in db.Technicians
                        select tech;

            foreach (var technician in query)
            {
                Technicians.Add(technician);
            }
        }

        IsLoaded = true;
    }
}