如何通過綁定來清除列表框的選定項目

Question

我有一個WPF ListBox通過ItemsSource綁定到集合。 所選項目以雙向模式綁定到VM上的屬性。 我想要在UI中爲模型屬性指定一個值時，在UI上「未選定」所選項目。

這可能嗎？如果沒有，可以選擇清除選定的項目嗎？

請記住我正在使用MVVM模式，所以我沒有從代碼中訪問列表本身。

謝謝！

Answer 1

我要去假定：

1. 你的ListBox的ItemsSource屬性綁定到您的視圖模型（即VM_List）一些名單。
2. 您的列表框的SelectedItem屬性綁定到您的ViewModel（即VM_SelectedItem）中的一些屬性與TwoWay綁定。

如果上述內容不準確，請詳細介紹一下您的實施情況。

您的視圖模型應該有一些代碼，看起來是這樣的：

public class VM : INotifyPropertyChanged 
{ 
    private ObservableCollection<Student> vmlist = new ObservableCollection<Student>(); 
    private Student vmselecteditem; 

    public event PropertyChangedEventHandler PropertyChanged; 

    public VM() 
    { 
     PropertyChanged = new PropertyChangedEventHandler(VM_PropertyChanged); 
    } 

    private void VM_PropertyChanged(object sender, PropertyChangedEventArgs e) 
    { 
    } 

    public ObservableCollection<Student> VM_List 
    { 
     get 
     { 
      return vmlist; 
     } 
    } 

    public Student VM_SelectedItem 
    { 
     get 
     { 
      return vmselecteditem; 
     } 
     set 
     { 
      vmselecteditem = value; 
     } 
    } 

    public void AddNewStudent(Student NewStudent) 
    { 
     VM_SelectedItem = null; 
     PropertyChanged(this, new PropertyChangedEventArgs("VM_SelectedItem")); 
     VM_SelectedItem = NewStudent; 
     SaveStudent(); 
     PropertyChanged(this, new PropertyChangedEventArgs("VM_SelectedItem")); 
     //The last line is optional, if you want to select the new student just added. 
    } 

    private void SaveStudent() 
    { 
     //A fake operation to save the student. 
     //To stick with MVVM, the save function should be in the model 
     //And this function should just call the one in the model. 
     BackgroundWorker b = new BackgroundWorker(); 
     b.DoWork += new DoWorkEventHandler(b_DoWork); 
     b.RunWorkerCompleted += new RunWorkerCompletedEventHandler(b_RunWorkerCompleted); 
     b.RunWorkerAsync(); 
    } 

    private void AddStudentToList() 
    { 
     VM_List.Add(VM_SelectedItem); 
    } 

    private void b_DoWork(object sender, DoWorkEventArgs e) 
    { 
     //Simulating a long save operation 
     System.Threading.Thread.Sleep(2000); 
    } 

    private void b_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) 
    { 
     AddStudentToList(); 
    } 
}