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!

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