Autopostback在ASP.NET中第一次无效？

我在更新面板中使用5个radiobutton，但是当我第一次检查radiobutton时，它不会进行检查更改 . 并且在那之后意味着第二次检查其工作正常，所以请告诉我应该是什么问题 . 这是我的代码

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
   <ContentTemplate>
       <asp:RadioButton ID="rbtn_A" runat="server" GroupName="rbt" 
            AutoPostBack="true" OnCheckedChanged="rbtn_A_CheckedChanged" />
       <asp:RadioButton ID="rbtn_B" runat="server" GroupName="rbt" AutoPostBack="true"
            OnCheckedChanged="rbtn_B_CheckedChanged" />
       <asp:RadioButton ID="rbtn_C" runat="server" GroupName="rbt" AutoPostBack="true" 
            OnCheckedChanged="rbtn_C_CheckedChanged" />
       <asp:RadioButton ID="rbtn_D" runat="server" GroupName="rbt" AutoPostBack="true" 
            OnCheckedChanged="rbtn_D_CheckedChanged" />
   </ContentTemplate>

这是我的第一个单选按钮c＃函数：protected void rbtn_A_CheckedChanged（object sender，EventArgs e）{

foreach (GridViewRow gv in dl_ques.Rows)
        {
            Label lblTest = (Label)gv.FindControl("lbltest");
            Label lbl = (Label)gv.FindControl("lbl_qno");
            RadioButton rbtn_A = (RadioButton)gv.FindControl("rbtn_A");
            DataSet ds = new DataSet();
            ds = getAnswer();
            SqlCommand cmd1 = DataManager.getCommandSp("spGetIBPSTestQues");
            cmd1.Parameters.AddWithValue("@Test_id", Convert.ToInt32(lblTest.Text));
            DataSet dsorg = DataManager.getDataSet(cmd1);
            if (ds.Tables[0].Rows.Count > 0)
            {
                SqlCommand cmd = new SqlCommand();
                cmd = DataManager.getCommandSp("SpUpdateIBPSTestSolved");
                cmd.Parameters.AddWithValue("@user_id", Convert.ToInt32(ht["UId"]));

                cmd.Parameters.AddWithValue("@Ans", "A");
                foreach (DataRow dr in dsorg.Tables[0].Rows)
                {
                    if (Convert.ToInt32(lbl.Text) == Convert.ToInt32(dr["actual_que"]))
                    {
                        if (dr["actual_ans"].ToString() == "A")
                        {
                            cmd.Parameters.AddWithValue("@Ans_correct", "Yes");
                        }
                        else
                        {
                            cmd.Parameters.AddWithValue("@Ans_correct", "No");
                        }
                    }
                }
                cmd.Parameters.AddWithValue("@test_id", Convert.ToInt32(lblTest.Text));
                cmd.Parameters.AddWithValue("@Test_dt", DateTime.Now);
                cmd.Parameters.AddWithValue("@Ques_id", lbl.Text);
                cmd.Parameters.AddWithValue("@LastTimeMin", timehdnmin.Value);
                cmd.Parameters.AddWithValue("@LastTimeSec", timehdnsec.Value);

                DataManager.WriteToDb(cmd);

            }
            else
            {
                SqlCommand cmd = new SqlCommand();
                cmd = DataManager.getCommandSp("SpInsertIBPSTestSolved");
                cmd.Parameters.AddWithValue("@user_id", Convert.ToInt32(ht["UId"]));

                cmd.Parameters.AddWithValue("@Ans", "A");
                foreach (DataRow dr in dsorg.Tables[0].Rows)
                {
                    if (Convert.ToInt32(lbl.Text) == Convert.ToInt32(dr["actual_que"]))
                    {
                        if (dr["actual_ans"].ToString() == "A")
                        {
                            cmd.Parameters.AddWithValue("@Ans_correct", "Yes");
                        }
                        else
                        {
                            cmd.Parameters.AddWithValue("@Ans_correct", "No");
                        }
                    }
                }

                cmd.Parameters.AddWithValue("@test_id", Convert.ToInt32(lblTest.Text));
                cmd.Parameters.AddWithValue("@Test_dt", DateTime.Now);
                cmd.Parameters.AddWithValue("@Ques_id", lbl.Text);
                cmd.Parameters.AddWithValue("@LastTimeMin", timehdnmin.Value);
                cmd.Parameters.AddWithValue("@LastTimeSec", timehdnsec.Value);

                DataManager.WriteToDb(cmd);
            }
        }
    }