Images in RTF getting lost on Mac

I have RTF text which I am showing to the user on Mac. Now I need to replace some text. The text has some images inline. When I execute the following code, the images are getting lost. I am using c#, Mono and Monobjc to run this on mac.

NSText _questionView;

// some initialisation code which I have skipped
//
NSRange range = NSRange.NSMakeRange(0, _questi开发者_高级运维onView.TextStorage.Length);
NSData oldString = _questionView.RTFFromRange(range);
if (oldString != null)
{
   string s = oldString.ConvertRTFToString();
   _questionView.ReplaceCharactersInRangeWithRTF(range, s.ConvertToNSData());
   _questionView.SelectedRange = NSRange.NSMakeRange(0,0); 
   // After this line the inline images are lost.
}

You are losing the images because you are converting the RTF content to NSString. NSString can only carry text, not attributes. You should consider using NSAttributedString instead for the text manipulation, in order to keep the RTF attributes (style, images, etc.).