c# - 访问DependencyProperty : The calling thread cannot access this object because a different thread owns it

Question

当DependencyProperty值更改时，我想将数据加载到WPF DataGrid中。我以为这样简单就可以了，但没有用。

public SQLiteDb.Attorney attorney
{
    get { return (SQLiteDb.Attorney)GetValue(attorneyProperty); }
    set {
        SetValue(attorneyProperty, value);
        GetAttorneysIdentitiesAsync(); //Load the data here.
    }
}
public static readonly DependencyProperty attorneyProperty =
    DependencyProperty.Register("attorney", typeof(SQLiteDb.Attorney),
      typeof(AttorneyDetails), new PropertyMetadata(new SQLiteDb.Attorney()));

但是我最终遇到了很少有经验的线程异常。方法 GetAttorneysIdentitiesAsync看起来像这样，我想它正在尝试从另一个线程访问属性值。

public async void GetAttorneysIdentitiesAsync()
{
    AlternativeIdentities = await SQLiteDb.db.Table<SQLiteDb.AttorneyIdentity>().Where(x => x.AttorneyId == attorney.Id).ThenBy(x => x.Id).Take(30).ToListAsync();
    AlternativeIdentitiesGrid.ItemsSource = AlternativeIdentities;
}

每当我尝试从属性类中访问属性时，都会得到异常。

The calling thread cannot access this object because a different thread owns it.

Answer 1

您应该在任务线程外部访问attorny属性:

public async Task GetAttorneysIdentitiesAsync()
{
    var id = attorney.Id;

    AlternativeIdentities = await SQLiteDb.db.Table<SQLiteDb.AttorneyIdentity>()
        .Where(x => x.AttorneyId == id)
        .ThenBy(x => x.Id)
        .Take(30)
        .ToListAsync();

    AlternativeIdentitiesGrid.ItemsSource = AlternativeIdentities;
}

还要注意，在依赖项属性的CLR包装器中，除了GetValue和SetValue之外，您不应调用其他任何东西。原因解释为 here。

您应该像这样注册一个PropertyChangedCallback:

public SQLiteDb.Attorney attorney
{
    get { return (SQLiteDb.Attorney)GetValue(attorneyProperty); }
    set { SetValue(attorneyProperty, value); }
}

public static readonly DependencyProperty attorneyProperty = DependencyProperty.Register(
    nameof(attorney), typeof(SQLiteDb.Attorney), typeof(AttorneyDetails),
    new PropertyMetadata(new SQLiteDb.Attorney(), attorneyPropertyChanged));

private static async void attorneyPropertyChanged(
    DependencyObject o, DependencyPropertyChangedEventArgs e)
{
    await ((AttorneyDetails)o).GetAttorneysIdentitiesAsync();
}