protected void Button2_Click(object sender, EventArgs e) 
{
　StringBuilder str = new StringBuilder(); 
　foreach (GridViewRow gvr in GridView1.Rows)
　{
　　string selectedText = ((DropDownList)gvr.FindControl("DropDownList1")).SelectedItem.Text;
　　str.Append(selectedText); 
　}
　Response.Write(str.ToString()); 
}