Question

I’m working on ASP.NET with C#.

I have a TextBox and I want to validate if the user is writing the correct length for the TextBox.

If the user is not entering the correct length I want a message to display on a label. But I want this check to happen on the fly, as the user is writing.

How can I do this?

Thanks.

Answer 1

suppose these are your asp.net elements

<asp:label id="message" runat="server"/><br/>
<asp:textbox runat="server" id="txtTest"/>

your js should be something like:

$(function(){
    $("input[id$='txtTest']").bind('keypress', function(){   
        if($("input[id$='txtTest']").val().length < 10)
            $("[id$='message']").text('incorrect length');
       else
        $("[id$='message']").text('');
    });
});

note that id$='message and input[id$='txtTest'] in jQuery means id ends with

When you mark an element to be run at server, asp.net append some other names at the start of the actual client id based on the name of you page.

and here is working demo