Transferring DataBound ID from aspx to codebehind

Question

I have an Unsubscribe page(Unsubscribe.aspx) that generates three radio buttons and a text field by using a repeater.

The id's of the radio buttons come from databinding and I need to get those ID's to use in the code page but I can't seem to get it to recognize the existence of this binding.

Unsubscribe.aspx looks like this:

                    <asp:Repeater ID="rptReasons" runat="server">
                        <HeaderTemplate>
                            <table>
                        </HeaderTemplate>
                        <ItemTemplate>
                            <div>
                                <div class="col-lg-12">
                                    <label class="radio-custom">
                                        <input id='rbReason<%# DataBinder.Eval(Container, "DataItem.ID")%>' type="radio" name="rbReason" value='<%# DataBinder.Eval(Container, "DataItem.ID")%>'>
                                        <i class="fa fa-circle-o"></i>
                                        <label for='rbReason<%# DataBinder.Eval(Container, "DataItem.ID")%>'><%# DataBinder.Eval(Container, "DataItem.Explanation")%></label>
                                    </label>
                                    <%# (DataBinder.Eval(Container.DataItem, "ReasonType").ToString() == "OTH") ? "<input class='form-control m-t m-l-n-md' name='txtComment' type='text' maxlength='100' style='width:300px;' />" : "" %>
                                </div>
                            </div>
                        </ItemTemplate>
                        <FooterTemplate>
                            </table>
                        </FooterTemplate>
                    </asp:Repeater>

And this is the behaviour I want to achieve:

            if (DataItem.ID == checked )
            {
                disable the text area
            }

Answer 1

try to add

runat="server"

<input runat="server" id='rbReason<%# DataBinder.Eval(Container, "DataItem.ID")%>' type="radio" name="rbReason" value='<%# DataBinder.Eval(Container, "DataItem.ID")%>'>

after that you need to find control on event

protected void Repeater1_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
    if (e.Item.ItemType == ListItemType.Item)
    {
        Label lbl = (Label)e.Item.FindControl("Label1");
        LinkButton link = (LinkButton)e.Item.FindControl("LinkButton1");
        RadioButton rdbtn = (RadioButton)e.Item.FindControl("control_id");
    }
}