Question

basically i got no idea to starts so i cant provide any better code
i have a null label

lblErrorMsg = "" ;

once if there are any error, my label will display error msg with css

lblErrorMsg.Text = "some error Msg";

at the same time i am trying to display another image label as well, but i dont want to make it like button click then display the error msg, due to this is an on-going project, so there are lot of button, so what i want to ask is, is there any method can perform during page load to detect label text change?

something like

pageload(){
    check lblErrorMsg
    if(lblErrorMsg.Text!=""){
         lblImg.Visible= true;
     }else{
         lblImg.Visible= false;
     }
}

Answer 1

You need to use javascript/Jquery for that. Listen to onload event and do the logic.

You can try putting this in the script tag of your aspx page

        window.onload = function(){
            var element = document.getElementById('<%=lblErrorMsg.ClientID%>');
            var lblMsg = document.getElementById('<%=lblImg.ClientID%>');
            lblMsg.style.display='none';
            if(element.innerHTML.length)
                 lblMsg.style.display = 'block';             
        }