dotnetable

PageMethods can be implemented by the following steps.

1. Include the Services namespace.

using System.Web.Services;

2. Add a public static method to your code behind page and decorate with [WebMethod].

[WebMethod]
public static string GetSalutation()
{
    var salutation = string.Empty;
    var hour = DateTime.Now.TimeOfDay.Hours;
    if (hour >= 0 && hour <= 11)
    {
         salutation = "Good Morning!";
    }
    else if (hour >= 12 && hour <= 16)
    {
        salutation = "Good Afternoon!";
    }
    else
    {
        salutation = "Good Evening!";
    }
     return salutation;
}

3. Add ScriptManager control from the Ajax Extensions tab on the Visual Studio toolbox.

4. Enable page methods in your app by adding EnablePageMethods=”true” to the Scriptmanager markup.

5. Write javascript to call the pagemethod and handle the result.

function GetGreeting()
{
    PageMethods.GetSalutation(onSucess, onError);

    function onSucess(result)
    {
        var ctrl = document.getElementById("Greeting");
        ctrl.value = result;
    }

    function onError(result)
    {
        alert('Cannot process your request at the moment, please try later.');
    }
}

6. Create an interface with elements for invoking the javascript method and displaying the results;

<input onclick="GetGreeting()" type="button" value="Go" />
<input id="Greeting" type="text" value="" />

Possible Issues

1. The scriptmanager must be placed inside the pages Form tags, it it is not an exception will be thrown;

‘ScriptManager’ must be placed inside a form tag with runat=server

2. If you miss off enabling the pagemethods on the scriptmanager a javascript error will be thrown;

‘PageMethods’ is undefined

Final Note

Interacting with page controls must be done in the javascript side as page controls cannot be accessed from with a pagemethod. So any values you need from page controls will need to be passed to the page methods as parameters.

I have added a visual studio project containing a couple of examples including the one above to Github.