DropDownList s SelectedIndexChanged event not firing

Question

I have a DropDownList object in my web page  When I click on it and select a different value  nothing happens  even though I have a function wired up to the SelectedIndexChanged event   First  the actual object s HTML code    lt asp DropDownList ID  logList  runat  server          onselectedindexchanged  itemSelected  gt   lt  asp DropDownList gt    And this is that function  itemSelected   protected void itemSelected object sender  EventArgs e        Response Write  Getting clicked      sender GetType   ToString         FileInfo selectedfile      Response Write   lt script gt alert  Hello   lt  script gt         foreach  FileInfo file in logs                if  file Name    logList Items logList SelectedIndex  Text                        Response Write   lt script gt alert  Hello   lt  script gt                         None of the Responses appear  and that portion of JavaScript is never run  I ve tried this on the latest 3 6 version of Firefox  as well as Internet Explorer 8  This is being served from a Windows Server 2003 R2 machine  running ASP NET with the  NET Framework version 4

User · Accepted Answer

Set  DropDownList AutoPostBack property to true   Eg    lt asp DropDownList ID  logList  runat  server  AutoPostBack  True           onselectedindexchanged  itemSelected  gt       lt  asp DropDownList gt

User · Answer

Also make sure the page is valid  You can check this in the browsers developer tools  F12   In the Console tab select the correct Target Frame and check for the  Page IsValid  property  If the page is not valid the form will not submit and therefore not fire the event

User · Answer

For me answer was aspx page attribute  i added Async  true  to page attributes and this solved my problem    lt    Page Language  C   MasterPageFile    MasterPage Reports Master            AutoEventWireup  true  Async  true    gt    This is the structure of my update panel   lt div gt     lt asp UpdatePanel ID  updt  runat  server  gt       lt ContentTemplate gt          lt asp DropDownList ID  id  runat  server  AutoPostBack  true         onselectedindexchanged  your server side function    gt       lt  ContentTemplate gt     lt  asp UpdatePanel gt   lt  div gt

User · Answer

I know its bit older post  but still i would like to add up something to the answers above   There might be some situation where in  the  value  of more than one items in the dropdown list is duplicated same  So  make sure that you have no repeated values in the list items to trigger this  onselectedindexchanged  event

User · Answer

try setting AutoPostBack  True  on the DropDownList

User · Answer

Instead of what you have written  you can write it directly in the SelectedIndexChanged event of the dropdownlist control  e g   protected void ddlleavetype SelectedIndexChanged object sender  EventArgs e       code goes here

User · Answer

Add property ViewStateMode  Enabled  and EnableViewState  true  And AutoPostBack  true  in drop DropDownList

[asp.net] DropDownList's SelectedIndexChanged event not firing

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