wpf - ComboBox 和实体框架，如何获取 ID？(WPF-MVVM)

Question

如何在 ViewModel.AddNewMovie() 中获取所选语言的 ID？这是我的第一次尝试。这很糟糕，因为它是索引，而不是 ID。

看法：

...
<ComboBox ItemsSource="{Binding LanguagesCollection}" 
SelectedIndex="{Binding NewMovieLanguage}"
DisplayMemberPath="L_Name" SelectedValuePath="L_Id"/>
...

视图模型：

...

public ObservableCollection<Languages> LanguagesCollection { get; private set; }
public ObservableCollection<Movies> MoviesCollection{ get; private set; }

...

_Entities = new MyAppEntities();
LanguagesCollection = new ObservableCollection<Languages>(_Entities.Languages);
MoviesCollection = new ObservableCollection<Movies>(_Entities.Movies.Include("Languages"));

...

private void AddNewMovie()
{
        OnPropertyChanged("NewMovieTitle");
        OnPropertyChanged("NewMovieLanguage");
    try
    {
        Movies NewMovie = new Movies 
        {
            M_Title = NewMovieTitle,
            M_Language_Id = Convert.ToInt32(NewMovieLanguage)+1,
        };

        _Entities.AddToMovies(NewMovie);
        MoviesCollection.Add(NewMovie);
        ...
    }
    catch
    {
        ...
    }
}

实体数据模型：

电影（表）

M_Id Int32

M_Title字符串

M_Language_Id Int32 fk

语言（表格）

L_Id Int32

L_Name字符串

- 数据 -

语言

1 英语

2 德语

3 法语

4 西班牙语

Answer 1

哦，解决方法是：

<ComboBox ItemsSource="{Binding LanguagesCollection}" 
SelectedValue="{Binding NewMovieLanguage}"
DisplayMemberPath="L_Name" SelectedValuePath="L_Id"/>

Answer 2

请更改为：

<ComboBox ItemsSource="{Binding LanguagesCollection}" 
SelectedItem="{Binding NewMovieLanguage}"
DisplayMemberPath="L_Name" SelectedValuePath="L_Id"/>