try
        {
            conn.Open();
            int a = cmd.ExecuteNonQuery();
            if (a == -1)
            {
                Response.Write("<script language=javascript>alert('添加失败');location='javascript:history.go(-1)'</script>");
            }
            else
            {
                //Response.Write("<script language=javascript>alert('添加成功');</script>");
            }
           

        }
        catch(Exception ex)
        {         
           // Response.Write("<script language=javascript>alert('"+ex.ToString()+"');location='Test.aspx'</script>");
            ScriptManager.RegisterStartupScript(udp1, typeof(UpdatePanel), "scriptname", "alert('" + ex.ToString() + "');", true);
        }

  this.ClientScript.RegisterStartupScript(this.GetType(), "", "alert('测试输出!')", true);

------解决方案--------------------
updatepanel里不能用this.GetType()，这里的this是Page，没用的，要用control:

protected void  DateTimePicker1_OnDateUpdated(object sender, EventArgs e)
{
ScriptManager.RegisterStartupScript(DateTimePicker1, DateTimePicker1.GetType(), "abc", "alert('good');", true);
}

------解决方案--------------------
 直接挂掉了 还弹什么？