ComboBox和Entity Framework，我如何获取ID？ （WPF-MVVM）

How do I get the Id of the selected language in the ViewModel.AddNewMovie()? This is my first try. It's bad, because it's the Index, and isn't the Id.

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。

View:

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

ViewModel:

...

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
    {
        ...
    }
}

Entity DataModel:

Movies (table)

M_Id Int32

M_Title String

M_Language_Id Int32 fk

M_Language_Id Int32 fk

Languages (table)

L_Id Int32

L_Name String

-- Data --

- 数据 -

Languages

1 English

2 German

3 French

4 Spanish

2 个解决方案

#1

Oh, the solution is:

哦,解决方案是:

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

#2

please change same as:

请改为:

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