Question

Having just added a new button in my web application, I get an error when clicking on it, and I’m wondering if this is related to misplaced code. I will describe what/where I did, briefly. Thanks very much.

In ascx file:

<asp:Button ID="btn_rezerv" runat="server" Text="Reserve film" OnClick="btn_rezerv_Click"/>  

In the ascx.cs file:

namespace CinProj.UserControls
{
    public partial class FilmsList : System.Web.UI.UserControl
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            PopulateControls();


        }

        private void PopulateControls()
        {
            string categId = Request.QueryString["CategID"];
            string filmId = Request.QueryString["FilmID"];
            ....


            if (categId != null)
            {
                .....
            }
            if (filmId != null)
            {
                ......
                Button btn_rezerv = (Button)item.FindControl("btn_rezerv");

            }


        }

        protected void btn_rezerv_Click(object sender, EventArgs e)
        {
            string fid = Request.QueryString["FilmID"];
            ShoppingCartAccess.AddItem(fid);
        }


    }
}

“Server Error in ‘/’ Application.

Invalid postback or callback argument. Event validation is enabled using in configuration or <%@ Page EnableEventValidation=”true” %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation. “

Answer 1

Another problem could be because your PopulateControls method should probably only be called when during the Page Load when it’s not a PostBack. I can’t tell from above, but to me it looks like it only needs done on Load. Try wrapping that call with this:

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {    
            PopulateControls();
        }
    }