Code
 //第一种情况：你要取GridView里的值且这个值在绑定的时候没有出现过
        ((DropDownList)GridView1.Rows[e.NewEditIndex].Cells[0].FindControl("fd")).Items.Add(GridView1.Rows[e.NewEditIndex].Cells[0].Text.ToString().Trim());
        ((DropDownList)GridView1.Rows[e.NewEditIndex].Cells[0].FindControl("fd")).SelectedValue = GridView1.Rows[e.NewEditIndex].Cells[0].Text.ToString().Trim();
        //第一种情况：你要取GridView里的值且这个值在绑定的时候出现
        ((DropDownList)GridView1.Rows[e.NewEditIndex].Cells[0].FindControl("fd")).SelectedValue = GridView1.Rows[e.NewEditIndex].Cells[0].Text.ToString().Trim();
        //第三种情况你就是你绑定的是个定值
        ((DropDownList)GridView1.Rows[e.NewEditIndex].Cells[0].FindControl("fd")).Items.Add("ksksksk");
        ((DropDownList)GridView1.Rows[e.NewEditIndex].Cells[0].FindControl("fd")).SelectedValue = "ksksksk";

protected void GridView1_RowCreated(object sender, GridViewRowEventArgs e)
  { 
  GridView g = (GridView)sender;
  if (g.Rows.Count == 0)
  {
  return;
  }
  DropDownList ddl = (DropDownList)g.Rows[g.Rows.Count-1].FindControl("ddl");
  if (ddl != null)
{
object[] array = new object[] { DateTime.Now.ToString() };
ddl.DataSource = array;
ddl.DataBind();

ddl.SelectedValue="";//你要设置的值

//自定义初始化操作
} 
}