无法访问动态创建的控件

Question

In my website I am able to create controls ( textbox and dropdown ) dynamically using UPDATE PANEL control. But I am unable to access these controls. Even while viewing in source code in the browser during debug, the dynamically created controls are absent! I am wondering how come we are able to see the dynamicallly created controls while the definition for them are absent in the source view of the o/p. Could you please clear my this doubt. Thanks a lot.

Code:

      <div id="divAssociatedInc">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
    <asp:UpdatePanel ID="UpdatePanel11" runat="server">
        <ContentTemplate>
            <%--<asp:UpdatePanel ID="updPnlAssociatedInc" runat="server" UpdateMode="Conditional">
                                                <ContentTemplate>--%>
            <asp:Label ID="lblcount" runat="server" Text="1" Visible="false"></asp:Label>
            <asp:Table ID="someTBL" runat="server" Style="width: 100%">
                <asp:TableRow>
                    <asp:TableCell HorizontalAlign="right" Style="width: 200px">
                        <asp:Label ID="lblAssociatedIncNo" runat="server" Text="Associated Incident(s)# :"></asp:Label><font
                            face="verdana" color="red" size="1"></font>

                        <div>
                            <asp:Button runat="server" ID="BtnAddAssoInc" OnClick="btnAddNewRowAssocInc_Click"
                                Text="Add Associated Incidents" />

                        </div>
                    </asp:TableCell>
                    <asp:TableCell HorizontalAlign="left" Style="width: 320px;">
                        <asp:TextBox ID="txtAssocIncRec0" name = "txtAssoc0" runat="server" MaxLength="12"></asp:TextBox>
                    </asp:TableCell>
                    <asp:TableCell HorizontalAlign="right" Style="width: 200px">
                        <asp:Label ID="lblAssociatedSeverity" runat="server" Text="Severity :"></asp:Label><font
                            face="verdana" color="red" size="1"></font>
                    </asp:TableCell>
                    <asp:TableCell HorizontalAlign="left" Style="width: 320px;">
                        <asp:DropDownList ID="ddlbAssocIncRec0" name="ddlbAssoc0" runat="server">
                        </asp:DropDownList>
                    </asp:TableCell>
                </asp:TableRow>

            </asp:Table>
        </ContentTemplate>
    </asp:UpdatePanel>

</div>

and the corresponding code behind is

        protected void Page_Load(object sender, EventArgs e)
    {
        int intRowCount = Convert.ToInt32(ViewState["No_of_Rows"]);
        for (int i = 1; i <= intRowCount; i++)
        {
            TableRow row = new TableRow();
            TableCell cell1 = new TableCell();
            TableCell cell2 = new TableCell();
            TableCell cell3 = new TableCell();
            TableCell cell4 = new TableCell();
            TextBox tb = new TextBox();
            DropDownList ddl = new DropDownList();
            Label lbl1 = new Label();
            Label lbl2 = new Label();

            row.ID = "rwAssocIncRec" + i;

            cell1.ID = "cAssocIncRec" + i + "1";
            cell2.ID = "cAssocIncRec" + i + "2";
            cell3.ID = "cAssocIncRec" + i + "3";
            cell4.ID = "cAssocIncRec" + i + "4";
            cell2.Attributes.Add("align", "left");
            cell4.Attributes.Add("align", "left");


            tb.ID = "txtAssocIncRec" + i;
            tb.MaxLength = 12;
            tb.EnableViewState = true;

            lbl1.ID = "lblAssocIncRec" + i + "01";
            lbl2.ID = "lblAssocIncRec" + i + "02";

            ddl.ID = "ddlbAssocIncRec" + i;

            cell1.Controls.Add(lbl1);
            cell2.Controls.Add(tb);
            cell3.Controls.Add(lbl2);
            cell4.Controls.Add(ddl);
            ddl.Items.Add(new ListItem("--Select--", "0"));
            ddl.Items.Add(new ListItem("1", "1"));
            ddl.Items.Add(new ListItem("2", "2"));


            row.Cells.Add(cell1);
            row.Cells.Add(cell2);
            row.Cells.Add(cell3);
            row.Cells.Add(cell4);

            someTBL.Rows.Add(row);
        }

    }
    protected void btnAddNewRowAssocInc_Click(object sender, EventArgs e)
    {

        TableRow newRow = new TableRow();
        newRow.ID = "trAssocIncRec" + lblcount.Text;

        TableCell newCell1 = new TableCell();
        newCell1.ID = "tdAssocIncRec1" + lblcount.Text;
        Label lbl = new Label();
        lbl.Text = "";
        lbl.ID = "lblAssocIncRec" + lblcount.Text;
        newCell1.Controls.Add(lbl);
        newRow.Cells.Add(newCell1);

        TableCell newCell2 = new TableCell();
        newCell2.ID = "tdAssocIncRec2" + lblcount.Text;
        TextBox txtBox = new TextBox();
        txtBox.ID = "txtAssocIncRec" + lblcount.Text;
        txtBox.MaxLength = 12;
        newCell2.Attributes.Add("align", "left");
        newCell2.Controls.Add(txtBox);
        newRow.Cells.Add(newCell2);

        TableCell newCell3 = new TableCell();
        newCell3.ID = "tdAssocIncRec3" + lblcount.Text;
        Label lbl2 = new Label();
        lbl2.Text = "";
        lbl2.ID = "lblAssocIncRec2" + lblcount.Text;
        newCell3.Controls.Add(lbl2);
        newRow.Cells.Add(newCell3);

        TableCell newCell4 = new TableCell();
        newCell4.ID = "tdAssocIncRec4" + lblcount.Text;
        DropDownList ddlb = new DropDownList();
        ddlb.ID = "ddlbAssocIncRec" + lblcount.Text;
        newCell4.Attributes.Add("align", "left");
        newCell4.Controls.Add(ddlb);
        ddlb.Items.Add(new ListItem("--Select--", "0"));
        ddlb.Items.Add(new ListItem("1", "1"));
        ddlb.Items.Add(new ListItem("2", "2"));
        newRow.Cells.Add(newCell4);

        someTBL.Rows.Add(newRow);
        ViewState["No_of_Rows"] = Convert.ToInt32(lblcount.Text);

        lblcount.Text = Convert.ToString(Convert.ToInt32(lblcount.Text) + 1);


    }

Answer 1

What you need to do is recreate these in either the Load event, or the Init event of the page every time. This is so that the values can be retrieved.

I would then find the controls you have created and add them to a list in a viewstate(so it gets destroyed when the user leaves the page)

ViewState["DynamicControls"] = list;

Then you have the values stored which you can come back to.