Why findcontrol("x") ASP.NET method can not find a HTML control that made via javascript runtime? -

my web page has optional contact panel user can add input text contact, cellphone or email,when user click create contact button, make input text attributes unique id(for example txtrelat1) or runat="server"(in client-side web page has input text id="txtrelat0" default) , when user click submit button ,calls register method in server-side onserverclick event, main question is,when use form1.findcontrol("txtrelat0"),it's find , can convert htmlinputtext when want form1.findcontrol("txtrelat1") it's not find , return null? thank's all

findcontrol finds server controls in page or control executing. deals server controls. code behind can still read values posted inputs add. call request.form["x"].

the downside if add additional controls page , postback server page isn't going "remember" elements added. they'll disappear after postback.

mixing types of client/server behaviors webforms isn't fun. might find easier server controls. set visible="false" or "true" in server code in response server events. or on client using api calls.

even though don't webforms much, when have work in webforms project it's easier things webforms way server controls.