string text = "Summary:" + Environment.NewLine + this.richTextBoxSummary.Text;
Clipboard.SetText(text);

Clipboard.SetText(richTextBox1.SelectedRtf, TextDataFormat.Rtf);

Clipboard.SetText(richTextBox1.SelectedText, TextDataFormat.UnicodeText);

richTextBox1.Copy();

DataObject dto = new DataObject();
dto.SetText(mesrtf, TextDataFormat.Rtf);
dto.SetText(mes, TextDataFormat.UnicodeText);
Clipboard.Clear();
Clipboard.SetDataObject(dto);

richTextBox1.Copy();

richTextBox1.Paste();