Adding text in RadRichTextBox and RadRichTextEditor is done via importing, not with the Text property. Here is how your code will look like:
(SqlDataReader dr = cmd.ExecuteReader())
radRichTextEditor1.Document = ImportString(text);
TxtFormatProvider provider =
Still, we do have a feature request for adding plain text or html text with the Text property. You can track its status and add your vote (like) for it here: http://feedback.telerik.com/Project/154/Feedback/Details/111956-add-radrichtextbox-init-the-content-using-text-property-with-support-of-html-f
As to using RadRichTextBox instead of RadRichTextEditor, I would strongly recommend using the latter, as it it a much better version of the editor control.
I hope that you find this information useful.
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