CODEWITHSUNDEEP
c#wpfmvvm
Justin Mathieu
Justin Mathieu

Reputation: 471

UriTypeConverter cannot convert from (null)

I'm running into the following NotSupportedException:

UriTypeConverter cannot convert from (null).

Here is the initial code where the error occurs:

SlideViewModel s = new SlideViewModel() { Duration = 8 };
_slideList.Add(s);
SlideView = CollectionViewSource.GetDefaultView(_slideList);
SelectedSlide = s; //This is where it crashes

_slideList is an ObservableCollection of SlideViewModels. SelectedSlide is a SlideViewModel.

Going into the setter for the SelectedSlide property, the code is:

set
{
     if (_selectedSlide != value)
     {
          _selectedSlide = value;
          RaisePropertyChanged("SelectedSlide");
      }
 }

Going even further into the RaisePropertyChanged function:

protected void RaisePropertyChanged(String propertyName)
{
     VerifyPropertyName(propertyName);
     OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}

And then OnPropertyChanged:

protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
{
     var handler = this.PropertyChanged;
     if (handler != null)
     {
          handler(this, e); //Crashes here!
     }
}

No idea whats happening. There's no inner exception.

Upvotes: 1

Views: 1521

Answers (1)

denis morozov
denis morozov

Reputation: 6316

You are ommiting you XAML binding code, but from the type of error, UriTypeConverter cannot convert from (null). Here's a possibility. If I am understanding correctly, SlideViewModel is type of SlideViewModel, somewhere, you bind in XAML to SlideViewModel.

//something like this?

that some property on SlideViewModel is probably a string. Uri expects a type of Uri. If that is correct, you need to create a converter that converts from Uri to String The use it in binding like:

<SomeElement Uri="{Binding SlideViewModel.SomeProperty,
                           Converter={StaticResource MyUriToStringConverter}",.../>

If you are alreading using a converter, make sure it handle nulls. Again, without xaml, or your target bindings, it is really hard to see who is responding to SlideViewModel's PropertyChanged event.

Upvotes: 1

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