从列表中删除项目后，ListView不会“刷新”

Question

我正在使用C＃编写Xamarin表单。我的列表视图能够显示数据库中的数据。我还在后面的代码中添加了带有点击事件处理程序的MenuItem。当我按住要删除（Android）的项目时，会调用MenuItem_Clicked并更新_students（我选择的项目已删除），但我的列表视图仍然没有“刷新”。

我的看法：

<ListView x:Name="listStudents" Refreshing="listStudents_Refreshing" 
                  IsPullToRefreshEnabled="True">
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <ViewCell>
                        <ViewCell.ContextActions>
                            <MenuItem Text="Delete" Clicked="MenuItem_Clicked" CommandParameter="{Binding .}" />
                        </ViewCell.ContextActions>
                        <StackLayout Padding="20">
                                <Label Text="{Binding Name}" />
                            </StackLayout>
                        </ViewCell>
                    </DataTemplate>
                </ListView.ItemTemplate>
        </ListView>

后面的代码：

  private ObservableCollection<Student> _students;

        public ListView_SearchBar()
    {
        InitializeComponent();
        var _students = SQLite_DB.SeedStudentData();
        _students = new ObservableCollection<Student>(_students);
        listStudents.ItemsSource = _students;
    }

        private void MenuItem_Clicked(object sender, EventArgs e)
    {
        listStudents.IsRefreshing = true;
        _students.Remove((sender as MenuItem).CommandParameter as Student);
        listStudents.ItemsSource = null;
        listStudents.ItemsSource = _students;
        listStudents.IsRefreshing = false;
        return;
    }

Answer 1

如果我按如下所示修改您的代码，则ListView会在我这一边正确更新：

private ObservableCollection<Student> _students;

public ListView_SearchBar()
{
    InitializeComponent();
    _students = SQLite_DB.SeedStudentData();
    _students = new ObservableCollection<Student>(_students);
    listStudents.ItemsSource = _students;
}

private void MenuItem_Clicked(object sender, EventArgs e)
{
    listStudents.IsRefreshing = true;
    _students.Remove((sender as MenuItem).CommandParameter as Student);
    listStudents.ItemsSource = null;
    listStudents.ItemsSource = _students;
    listStudents.IsRefreshing = false;
    return;
}

请注意，我在页面构造函数中删除了第一次使用var的_student签名。