Drop ASP.Net Drop Down SelectedIndex_Changed Not Working

Question

I have the following code for the DropDown Selected Index Changed. But It's not firing the event as expected

<asp:DropDownList ID="DropCourseLevel" runat="server" CssClass="form-control m-input" 
AutoPostBack="true" OnSelectedIndexChanged="DropCourseLevel_SelectedIndexChanged" >
</asp:DropDownList>

I'm getting the following error in the Console

Uncaught Error: Sys.WebForms.PageRequestManagerServerErrorException: 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.

Any Help is much appreciated

Look at your `Page_Load`. I guess there is code which databinds the page and this dropdown. Do that only `if(!IsPostBack)`. — Tim Schmelter, Mar 22 '18 at 15:01
Have you serached this error on stackoverflow? You will find the answer. Do you change the content of the dropdown via javascript? — Tim Schmelter, Mar 22 '18 at 15:07
@TimSchmelter I was Able to resolve the Issue by adding EnableEventValidation="false" on my page's code. Thanks For the Response — Jayasurya Satheesh, Mar 22 '18 at 15:19

score 2 · Accepted Answer · answered Mar 22 '18 at 15:17

2

Try Setting this property on your aspx page as:

EnableEventValidation="false"

answered Mar 22 '18 at 15:17

Hussein Salman

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Thanks. That Solved My Issue – Jayasurya Satheesh Mar 22 '18 at 15:18
Related answer (with more background info): https://stackoverflow.com/q/1503630/1220550 – Peter B Mar 22 '18 at 15:24
Thanks for the Info @PeterB. i really appreciate your help – Jayasurya Satheesh Mar 23 '18 at 05:16

score 0 · Answer 2 · answered Mar 22 '18 at 15:18

I was Able to resolve the Issue by adding EnableEventValidation="false" on my page's code

<%@ Page Language="C#" AutoEventWireup="true" EnableEventValidation="false" 
CodeBehind="Application.aspx.cs" Inherits="USI.User.Application" 
Title="Course Application" MasterPageFile="~/User/MyPage.Master" %>

Drop ASP.Net Drop Down SelectedIndex_Changed Not Working

2 Answers2