drag and drop

Code:

---

private void rtbInterop_DragDrop(object sender, System.Windows.Forms.DragEventArgs e)
                {
                        if(e.Data.GetDataPresent(DataFormats.Text))
                        {
                                rtbInterop.Text = e.Data.GetData(DataFormats.Text).ToString();
                        }
                        else if(e.Data.GetDataPresent(DataFormats.FileDrop))
                        {
                                rtbInterop.Text = e.Data.GetData(DataFormats.FileDrop).ToString(); // Does not work
                        }
                }

---

This enables me to copy or move any text from another
application into this RichTextBox.
The second thing is: to drag a file into the textbox and
then display the content of that file in textform in the
RichTextBox.

How could I do this?

thx!