paste image from clipboard to wpf richtextbox problem

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C#

WPF

C#4.0

hello....

I an working on wpf richtextbox control i want to inster image in each paragraph
and insert (Text+Image) into sql table.


i have problem while i try to paste image on richtextbox some time it work some time doesn't show anything...

OpenFileDialog dlg = new OpenFileDialog();
                dlg.Title = "Add image";
                dlg.Filter = "png,jpg|*.png;*.jpg";
                if (dlg.ShowDialog() == true)
                {
                    System.Threading.Thread.Sleep(20);
                    var clipboard = Clipboard.GetDataObject();
                    BitmapImage bitmapImage = SetImage(dlg.FileName);
                    Clipboard.SetImage(bitmapImage);
                    txt.Paste();
                    Clipboard.SetDataObject(clipboard);
                }


private BitmapImage SetImage(String filename)
        {
            BitmapImage bi = new BitmapImage();
            if (System.IO.File.Exists(filename))
            {
                bi.BeginInit();
                bi.CacheOption = BitmapCacheOption.OnLoad;
                bi.CreateOptions = BitmapCreateOptions.IgnoreImageCache;
                bi.UriSource = new Uri(filename);
                bi.EndInit();
            }
            return bi;
        }

pls help..... let me know why this is not working where i am wrong.....
with this code...

[Edit]Code block added[/Edit]