小编paw*_*8hp的帖子

在我的应用程序中,我有讲师,他们有可以教授的课程列表,当我删除课程时,我想删除与讲师的联系.这是代码:

public void RemoveCourse(int courseId)
{
    using (var db = new AcademicTimetableDbContext())
    {
        var courseFromDb = db.Courses.Find(courseId);

        var toRemove = db.Lecturers
                        .Where(l => l.Courses.Contains(courseFromDb)).ToList();

        foreach (var lecturer in toRemove)
        {
            lecturer.Courses.Remove(courseFromDb);
        }

        db.SaveChanges();
    }
}

但它不起作用.我明白了

NotSupportedException:无法创建类型的常量值Course.在此上下文中仅支持基元类型或枚举类型.

我究竟做错了什么？

我正在为我的项目使用MVVM,并且我正在尝试使用DataGrid将数据库中的表绑定.但是当我运行我的应用程序时,datagrid是空的.

MainWindow.xaml.cs:

 public MainWindow(){
        InitializeComponent(); 
        DataContext = new LecturerListViewModel()
    }

MainWindow.xaml:

 <DataGrid AutoGenerateColumns="False" ItemsSource="{Binding Source=Lecturers}" >
            <DataGrid.Columns>
                <DataGridTextColumn Header="Name" Binding="{Binding Name}"/>
                <DataGridTextColumn Header="Surname" Binding="{Binding Surname}"/>
                <DataGridTextColumn Header="Phone" Binding="{Binding Phone_Number}" />
            </DataGrid.Columns>
 </DataGrid>

LecturerListViewModel.cs:

public class LecturerListViewModel : ViewModelBase<LecturerListViewModel> 
{

    public ObservableCollection<Lecturer> Lecturers;
    private readonly DataAccess _dataAccess = new DataAccess();

    public LecturerListViewModel()
    {
        Lecturers = GetAllLecturers();
    }

和ViewModelBase实现INotifyPropertyChanged.

Lecturer.cs

public class Lecturer
{
    public Lecturer(){}

    public int Id_Lecturer { get; set; }
    public string Name { get; set; }
    public string …