c# - InvalidCastException : Unable to cast object of type 'Mocks.Class_…' to 'Class'

Question

在我的WPF MVVM项目中，出现此错误:

InvalidCastException: Unable to cast object of type 'Mocks.DDD_AutoRadio_General_Audio_AudioFile_130_13063066' to type 'DDD.AutoRadio.General.Audio.AudioFile'.

WPF MainWindow具有自定义的 UserControl。

简化的类 AudioFile:

namespace DDD.AutoRadio.General.Audio
{
    [DataContract]
    public class AudioFile : INotifyPropertyChanged
    {
        private string name;
        /// <summary>
        /// Name of the Mp3
        /// </summary>
        [DataMember]
        public string FilePath
        {
            get { return name; }
            set
            {
                var oldvalue = name;
                if (oldvalue != value)
                {
                    name = value;
                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("FilePath"));
                 }
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
    }
}

但我认为这与此类无关。
我认为更多是在自定义 UserControl中:

public partial class EditField : UserControl
{
    public static DependencyProperty selectedList = 
        DependencyProperty.Register("DataGridSelectedItems", typeof(OC<AudioFile>), typeof(EditField));


    public OC<AudioFile> DataGridSelectedItems
    {
        get { return (OC<AudioFile>)GetValue(selectedList); }
        set { SetValue(selectedList, value); }
    }

    public EditField()
    {
        InitializeComponent();
    }

    private void Collection_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        OC<AudioFile> l = new OC<AudioFile>();
        foreach (AudioFile i in Collection.SelectedItems) //'Collection' is a DataGrid
            l.Add(i);
        DataGridSelectedItems = l;
    }
}

注意:OC是基于 ObservableColletion<>类的类

public class OC<T> : ObservableCollection<T> where T: INotifyPropertyChanged

这是StackTrace

at DDD.AutoRadio.Database.Editor.View.EditField.Collection_SelectionChanged(Object sender, SelectionChangedEventArgs e)
at System.Windows.Controls.SelectionChangedEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
at System.Windows.UIElement.RaiseEvent(RoutedEventArgs e)
at System.Windows.Controls.DataGrid.OnSelectionChanged(SelectionChangedEventArgs e)
at System.Windows.Controls.Primitives.Selector.InvokeSelectionChanged(List`1 unselectedInfos, List`1 selectedInfos)
at System.Windows.Controls.Primitives.Selector.SelectionChanger.End()
at System.Windows.Controls.Primitives.Selector.SelectionChanger.SelectJustThisItem(ItemInfo info, Boolean assumeInItemsCollection)
at System.Windows.Controls.Primitives.Selector.SetSelectedToCurrent()
at System.Windows.Controls.Primitives.Selector.SetSynchronizationWithCurrentItem()
at System.Windows.Controls.DataGrid.OnItemsSourceChanged(IEnumerable oldValue, IEnumerable newValue)
at System.Windows.Controls.ItemsControl.OnItemsSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
at System.Windows.DependencyObject.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.FrameworkElement.OnPropertyChanged(DependencyPropertyChangedEventArgs e)
at System.Windows.DependencyObject.NotifyPropertyChange(DependencyPropertyChangedEventArgs args)
at System.Windows.DependencyObject.UpdateEffectiveValue(EntryIndex entryIndex, DependencyProperty dp, PropertyMetadata metadata, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, Boolean coerceWithDeferredReference, Boolean coerceWithCurrentValue, OperationType operationType)
at System.Windows.DependencyObject.InvalidateProperty(DependencyProperty dp, Boolean preserveCurrentValue)
at System.Windows.Data.BindingExpressionBase.Invalidate(Boolean isASubPropertyChange)
at System.Windows.Data.BindingExpression.TransferValue(Object newValue, Boolean isASubPropertyChange)
at System.Windows.Data.BindingExpression.Activate(Object item)
at System.Windows.Data.BindingExpression.AttachToContext(AttachAttempt attempt)
at System.Windows.Data.BindingExpression.MS.Internal.Data.IDataBindEngineClient.AttachToContext(Boolean lastChance)
at MS.Internal.Data.DataBindEngine.Task.Run(Boolean lastChance)
at MS.Internal.Data.DataBindEngine.Run(Object arg)
at MS.Internal.Data.DataBindEngine.OnLayoutUpdated(Object sender, EventArgs e)
at System.Windows.ContextLayoutManager.fireLayoutUpdateEvent()
at System.Windows.ContextLayoutManager.UpdateLayout()
at System.Windows.UIElement.UpdateLayout()

Answer 1

我找到了解决方案:

在自定义UserControl EditField中，存在DependentieProperty的SelectedItems'DataGridItemsSource'。

我需要做的就是从源中选择对象，而不是从SelectedItems中选择对象。

(在Class AudioFile中，我还有一个属性“Songcode”)

public partial class EditField : UserControl
{
    #region DataGridSelectedItems
    public static DependencyProperty selectedList = 
        DependencyProperty.Register("DataGridSelectedItems", typeof(OC<AudioFile>), typeof(EditField));


    public OC<AudioFile> DataGridSelectedItems
    {
        get { return (OC<AudioFile>)GetValue(selectedList); }
        set { SetValue(selectedList, value); }
    }
    #endregion

    #region DataGridItemsSource
    public static DependencyProperty datagriditemsource =
        DependencyProperty.Register("DataGridItemsSource", typeof(OC<AudioFile>), typeof(EditField));

    public OC<AudioFile> DataGridItemsSource
    {
        get { return (OC<AudioFile>)GetValue(datagriditemsource); }
        set { SetValue(datagriditemsource, value); }
    }
    #endregion

    public EditField()
    {
        InitializeComponent();
}

    private void Collection_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        OC<AudioFile> l = new OC<AudioFile>();
        DataGridSelectedItems.Clear();
        foreach (AudioFile i in Collection.SelectedItems) //'Collection' is a DataGrid
             l.Add(DataGridItemsSource.Where(x => x.Songcode == i.Songcode || x.FilePath == i.FilePath).First());
        If (l.Count > 0)
            DataGridSelectedItems = l;
    }
}