>On the same page I have a GridView bound to a dataset. Below the GridView there is a textbox (or several textboxes). As user navigates through the GridView (clicking on this or that row) I want the value/text in the textbox(s) to be updated according to new row in the dataset. My understanding is I need to bind the textbox(s) to the same dataset. How do you do it? An example, of one textbox binding to the dataset would be very helpful.

If you don't mind round-tripping to the server you can wire up the GridView.SelectedIndexChanged event and do something like this:

protected void GridView1_SelectedIndexChanged(object sender, EventArgs e)
        {
            TextBox1.Text = GridView1.SelectedRow.Cells[2].Text;
            //etc
        }