WebMethod Example

I want a label box to be refreshed every one second with a random number generated at the server

This is a classic example of WebMethods. WebMethods are written on the server side in the page class. WebMethods are static. Here is a simple implementation of a webmethod:

private static Random random = new Random(1000);

[WebMethod]
public static int GetRandomNumber()
{
    return random.Next(10, 99);
}

To be able to call this WebMethod from Javascript, the asp:ScriptManager should have the EnablePageMethods property set to true:

<form id="form1" runat="server">
<asp:ScriptManager runat="server" EnablePageMethods="true"></asp:ScriptManager>
<asp:Label ID="Random" runat="server"></asp:Label>
</form>

From Javascript, the WebMethod can be called using the syntax PageMethods.FunctionName(Arg0, Arg1, OnSucceededCallBack); WebMethods are executed asynchronously. So a callback function has to be provided. Here is an example of updating a label box with the random number

<script type="text/javascript">

    setTimeout("PageMethods.GetRandomNumber(setRandom);", 1000);

    function setRandom(result) {
        document.getElementById("Random").innerText = result;
        setTimeout("PageMethods.GetRandomNumber(setRandom);", 1000);
    }
        
</script>