在ASP.net AJAX中使用Javascript事件

Question

I can't believe that this hasn't been covered before, but I have been having a hard time finding an answer to this one on Google.

I am learning AJAX with ASP.NET, and I have a working prototype. My only problem is that I want to kick off my AJAX validation on a JavaScript event (onKeyUp to be exact) however, ASP.NET seems to only support its server side events for its version of AJAX. How do I call my AJAX from a client side event?

Thanks

UPDATE

Just wanted to add that I did find this trick out there, but this causes the website to do a postback, which makes no sense to me if your trying to do AJAX.

txtFirstName.Attributes.Add("onKeyUp","__doPostBack('ctl00_ContentPlaceHolder1_txtFirstName','')");

Answer 1

It sounds like you're doing Web Forms stuff and you want to validate some content as its being typed or at least after they submit the data.

You might want to take a look at the ASP.NET Ajax Toolkit. You can download the .dll and add it as a reference to your project.

Take a look at the ValidatorCallOut

Answer 2

Ok, so I "Borrowed" this code from w3Schools.com, So I want to give them credit

<script type="text/javascript">
  function val() {
    var xmlhttp;
    if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari
        xmlhttp = new XMLHttpRequest();
    }
    else {// code for IE6, IE5
        xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    xmlhttp.onreadystatechange = function() {
        if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
            document.getElementById("spnFirstName").innerHTML = xmlhttp.responseText;
        }
    }
    xmlhttp.open("POST", "server.aspx", true);
    xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    xmlhttp.send();
    //xmlhttp.send("fname=Henry&lname=Ford"); //This is if you want to send values
  }
</script>



First Name: <asp:TextBox ID="txtFirstName" runat="server" OnTextChanged="txtFirstName_TextChanged" AutoPostBack="True" onkeyup="Val()"></asp:TextBox>
<span id="spnFirstName" runat="server" style="color:Red"> </span>

Server.aspx is an empty page that just has the word "Hello" in it. As you can see, I tied this simple javascript function to the onKeyUp Event. This also seems not to interfer with the ASP.NET AJAX validation.

I like doing this much better than adding a dll, because as long as I stick with the core asp.net product, I don't have to worry about other developers having to dig up libraries they might not have.