当control.find（id）用于查找动态生成的单选按钮时，radiobutton checked属性始终为false

Question

我已经动态添加单选按钮到webform，如下所示。 在提交时单击，当我尝试使用control.find（radiobuttonid）查找无线电检查属性时。即使选中单选按钮，它也始终返回false。有些人能帮助我怎么做吗？

                        RadioButton r1 = new RadioButton();
                        r1.ID = "r1" + i.ToString();
                        r1.GroupName = "radio";
                        PlaceHolder1.Controls.Add(r1);
                        Label t1 = new Label();
                        t1.ID = "t1" + i.ToString();
                        t1.Text = ReturnCode["ans1"].ToString();
                        PlaceHolder1.Controls.Add(t1);
                        PlaceHolder1.Controls.Add(
         new LiteralControl("\r\n<br /> \r\n"));
                        RadioButton r2 = new RadioButton();
                        r2.GroupName = "radio";
                        r2.ID = "r2" + i.ToString();
                        PlaceHolder1.Controls.Add(r2);
                        Label t2 = new Label();
                        t2.ID = "t2" + i.ToString();
                        t2.Text = ReturnCode["ans2"].ToString();
                        PlaceHolder1.Controls.Add(t2);
                        PlaceHolder1.Controls.Add(
         new LiteralControl("\r\n<br /> \r\n"));

                        RadioButton r3 = new RadioButton();
                        r3.ID = "r3" + i.ToString();
                        r3.GroupName = "radio";
                        PlaceHolder1.Controls.Add(r3);

                        Label t3 = new Label();
                        t3.ID = "t3" + i.ToString();
                        t3.Text = ReturnCode["ans3"].ToString();
                        PlaceHolder1.Controls.Add(t3);
                        PlaceHolder1.Controls.Add(
         new LiteralControl("\r\n<br /> \r\n"));
                        RadioButton r4 = new RadioButton();
                        r4.ID = "r4" + i.ToString();
                        r4.GroupName = "radio";
                        PlaceHolder1.Controls.Add(r4);
                        Label t4 = new Label();
                        t4.ID = "t4" + i.ToString();
                        t4.Text = ReturnCode["ans3"].ToString();
                        PlaceHolder1.Controls.Add(t4);
                        PlaceHolder1.Controls.Add(
      new LiteralControl("\r\n<br /> \r\n"));