Cannot retrieve RichTextBox contents stored in a database

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C#

SQL-Server

RichTextBox

I am trying to read to contents of the rich text box (which includes images) i stored my database but i keeps returning an exception.

"An unhandled exception of type 'System.ArgumentException' occurred in System.Windows.Forms.dll Additional information: File format is not valid."

cmd=new SqlCommand("select question from questions where id=1",connx);
 SqlDataReader dr = cmd.ExecuteReader();
 if (dr.Read())
 {
      Byte[] rtf = new Byte[Convert.ToInt32(dr.GetBytes(0, 0, null, 0, Int32.MaxValue))];

      long bytesReceived = dr.GetBytes(0, 0, rtf, 0, rtf.Length);

      ASCIIEncoding encoding= new ASCIIEncoding();

      question.Rtf = encoding.GetString(rtf, 0, Convert.ToInt32(bytesReceived));
 }