Making gridview column as hyperlink

On top of Martin's approach you can use a label and keep your field as boundfield. But his approach is the correct way. Just saying mine will not be the best approach but it is still another solution to your question:

for (int i = 0; i < GridView1.Rows.Count; i++) // Loop each row in the gridview
{
  Label lbtn = new Label(); //Create the label
  lbtn.CssClass = "lbtnStyle"; 
  lbtn.ID = "lbtn" + GridView1.Rows[i].Cells[2].Text; // Give an ID to the label
  lbtn.Text = GridView1.Rows[i].Cells[2].Text; 
  lbtn.Attributes.Add("onClick", "javascript:window.open('Default.aspx')");
  GridView1.Rows[i].Cells[2].Controls.Add(lbtn); // Choose the cell to add the label
}

Good luck,
OI