System.InvalidOperationException with RadRichTextbox from Telerik in WPF

If you have an HTML document that you import into the RadRichTextbox that has images and you are hosting WPF within MFC (c++), then you are probably running into this issue. Right along with all the people who have a steering wheel on the right side of the car driving around in the States. Yeah, all 1 of us.

Anyway, it’s an issue for us but here is the work around since Telerik will probably be slow to fix it, if they do. Quick backstory, they  load the images using WebClient instead of loading from disk. Better yet, they use the async methods on the webclient with a callback. We all know how much WPF loves stuff from other threads.

Here is the fix.


  {//.........some function some where in time.
  var formatter = new HtmlFormatProvider();//The thing you use to load your html
    formatter.ImportSettings.LoadImageFromUrl += ImportSettings_LoadImageFromUrl;
    var doc = formatter.Import(html);//html is your variable with your html....from whereever
    boxxy.Document = doc;//boxxy is my richtextbox instance
 //the meat and potato's 
void ImportSettings_LoadImageFromUrl(object sender, LoadImageEventArgs e)
    using (var file = new FileStream(e.Url, FileMode.Open))
        e.ImageElement.UriSource = null;//prevent them from trying to load in background
        e.ImageElement.Init(file, Path.GetExtension(e.Url));//load from our stream
        e.ImageElement.ImageSource.Freeze();//prevent cross thread issue by freezing it.
    e.Handled = true;


Happy Coding!

The type initializer for +’System.Windows.PresentationSource’ threw an exception.

I had an issue with a 3rd party control. I couldn’t blame them too much since the issue only happened in the WPF control hosted in a MFC C++ application. brutal for sure.

Why host WPF in C++? That is a question for another time, but let’s just say its an app written in the early 90’s and still has been rewritten, just bolted on and refactored.

Well, I created the test application and it worked great on my machine at home. I loaded it into my work computer and blammo, it threw up on the get handle call. WTF?

If you step into the .NET source(slow but very helpful), you get this.

System.Runtime.Versioning.BinaryCompatibility.ParseTargetFrameworkMonikerIn/toEnum in the call stack. and  NULL parameter exception.

Turns out through some goofiness in VC++, it will insert a null value in a manifest.

The fix is really easy. Delete all the files in your AppData\Local\Temp folder under your profile.

Here is a link to a guy who wrote about it in much more detail, but man that was non-intuitive fix. It worked though, so I am happy!

Thanks Microsoft for stealing another hour of my life. Thanks Telerik for being there to steal a week trying to reproduce bugs in your silly slow controls.

Happy coding!