Question

This seems like an elementary issue but it has me stumped.

I have a main page which loads a custom control (.ascx) on page_load.

This custom control has two fields. One of them being a dropdownlist and the other being a text box. When the dropdownlist changes value it triggers a post back, some logic is executed server side and a value is generated for the textbox. I stepped through the code and the value is created and assigned correctly. However, when the page is rendered the value does not change.

If I change the textbox value to “QQQ” and trigger the postback, “QQQ” stays in the textbox so I can verify viewstate is working.

Is there any reason why the generated value is not being displayed in the form on postback. This process works fine on the initial page load.

.aspx.cs

protected void Page_Load(object sender, EventArgs e)
{
   string ascxPath = @"~/_CONTROLTEMPLATES/TRC_BITS.ascx";
   TRC_BITS control = Page.LoadControl(ascxPath) as TRC_BITS;
   phForm.Controls.Add(control);
}

.ascx

   <asp:TextBox ID="message" runat="server" TextMode="MultiLine" /><br/>
   <asp:DropDownList ID="year" runat="server" AutoPostBack="true">
      <asp:ListItem Text="2011">2011</asp:ListItem>
      <asp:ListItem Text="2012">2012</asp:ListItem>
      <asp:ListItem Text="2013">2013</asp:ListItem>
   </asp:DropDownList>

.ascx.cs

protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
    {
        year.SelectedValue = DateTime.Now.Year.ToString();
    }
    if (year.SelectedValue == 2012)
       message.Text = "ABC";
    else
       message.Text = "XYZ";
}

Answer 1

Because you are adding the controls dynamically, you need to add them during the page’s oninit event.
Try it, believe me. Go for it. Yalla.