<Window ... DataContext="{Binding EmployeesViewModel, Source={StaticResource ViewModelLocator}}">
    <Grid x:Name="LayoutRoot">
        <DataGrid ItemsSource="{Binding Path=Employees}" AutoGenerateColumns="False" HorizontalAlignment="Stretch">
            <DataGrid.Columns>
                <DataGridTextColumn IsReadOnly="True" Header="Фамилия" Binding="{Binding Path=LastName}" Width="100" />
                <DataGridTextColumn IsReadOnly="True" Header="Имя" Binding="{Binding Path=FirstName}" Width="*" />
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</Window>

public class ViewModelLocator
{
    private readonly Lazy<EmployeesViewModel> employeesViewModel = new Lazy<EmployeesViewModel>();
    public EmployeesViewModel EmployeesViewModel { get { return employeesViewModel.Value; } }        
}

public class EmployeesViewModel
{
    private readonly IDataContext Context;
    public EmployeesViewModel()
    {
        Context = Ioc.Default.GetInstance<IDataContext>();
    }

    public IEnumerable<Employee> Employees { get { return Context.Employees.ToList(); } }
}