Question

I did my drop down list that get its values from the database and when running the application, it did not work and the compiler did not see the code.

// aspx

  <asp:UpdatePanel ID="UpdatePanel3" runat="server">
                 <ContentTemplate>
                       <asp:DropDownList ID="DDlProductFamily" runat="server"
                         ondatabound="DDlProductFamily_DataBound"
                         onselectedindexchanged="DDlProductFamily_SelectedIndexChanged">
                                                </asp:DropDownList>
                                            </ContentTemplate>
                                            <Triggers>
                                                <asp:AsyncPostBackTrigger ControlID="DDlProductFamily" EventName="SelectedIndexChanged" />
                                            </Triggers>
                                        </asp:UpdatePanel>

// cs

 protected void DDlProductFamily_SelectedIndexChanged(object sender, EventArgs e)
    {
        using (SqlConnection Con = Connection.GetConnection())
        {
            SqlCommand Com = new SqlCommand("SelectThumbByProductFamily", Con);
            Com.CommandType = CommandType.StoredProcedure;
            Com.Parameters.Add(Parameter.NewInt("@ProductCategory_Id",
                DDlProductFamily.SelectedValue.ToString()));
            SqlDataAdapter DA = new SqlDataAdapter(Com);
            DA.Fill(dt);
            DataList1.DataSource = dt;
            DataList1.DataBind();
        }
    }

Answer 1

Check if listbox has property AutoPostBack=”True”.