Subscribe to events of an existing RichTextContentControl

Question

I'm trying to access all Rich-Text-Content-Controls of an existing .docx Document (Office Open XML).

I've found a way to get all Content Controls of a Document by looping over a specified range:

var contentControls = new List<ContentControl>();
Range rangeStory;
foreach (Range range in wordDocument.StoryRanges)
{
    rangeStory = range;
    do
    {
        try
        {
            contentControls.AddRange(rangeStory.ContentControls.Cast<ContentControl>());
        }
        catch (COMException) { }
        rangeStory = rangeStory.NextStoryRange;
    }
    while (rangeStory != null);
}

But I can't find a way to cast these ContentControls (assembly: Microsoft.Office.Interop.Word) to RichTextContentControls (assembly: Microsoft.Office.Tools.Word).

RichTextContentControl richTextContentControl = contentControl as RichTextContentControl;
throws Exception

I want to do this casting, because I need to subscribe to RichTextContentControl's entering and exiting events.

richTextContentControl.Entering += (sender, args) => {/*..*/ };
richTextContentControl.Exiting += (sender, args) => {/*..*/ }; 

Answer 1

Found it! There is a very easy way to access any kind of Content Controls via Vsto:

foreach (var result in thisDocument.Controls.OfType<RichTextContentControl>())
{
    result.Entering += (sender, args) =>
    {
        MediatorContext.Current.Send(new CurrentKomponenteChangedRequest(result.ID, State.Entering));
    };

    result.Exiting += (sender, args) =>
    {
        MediatorContext.Current.Send(new CurrentKomponenteChangedRequest(result.ID, State.Exiting));
    };
}