Question

我有一个针对FCU的UWP应用。从今天起我得到以下例外：

System.InvalidCastException: Unable to cast COM object of type 'System.__ComObject' to class type 'System.String'. Instances of types that represent COM components cannot be cast to types that do not represent COM components; however they can be cast to interfaces as long as the underlying COM component supports QueryInterface calls for the IID of the interface.
   at MoneyFox.Windows.Views.AccountListView.AccountListView_obj1_Bindings.Update_CurrentBalance(Double obj, Int32 phase)
   at MoneyFox.Windows.

据我所知，只要对TextBlock的double类型的绑定应该更新，就会发生这种情况。但是我对这段代码没有任何改变。

我有最新的VS 15.7.3。此外，我尝试针对不同的平台和不同版本的Microsoft.NETCore.UniversalWindowsPlatform（目前为6.0.8）。

存储库链接：https://github.com/NPadrutt/MoneyFox.Windows/tree/XamarinFormsNew

那可能是什么？

Answer 1

我发现了问题..我有一个转换器，它通过Xamarin.Forms实现IValueConverter以及继承自MvxValueConverter，所以我可以将它用于Xamarin Forms Bindings以及我的UWP应用程序而不用XF。

public class AmountFormatConverter : MvxValueConverter, IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        // Converter Logic
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) 
    {
        // Convert Back Logic
    }
}

我的问题是，我没有为已实现的方法设置Override关键字。这似乎引起了这个问题。

public class AmountFormatConverter : MvxValueConverter, IValueConverter
{
    public override object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        // Converter Logic
    }

    public override object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) 
    {
        // Convert Back Logic
    }
}

UWP System.InvalidCastException：无法转换COM对象

1 个答案: