How to use MS Ajax PageMethods to call a function on the server

I have a project that uses PageMethods to call functions on the server. The server functions (written in C#) return the values as array of strings, without doing any kind of serialization and in the client side (from Js) the accessing of the return values is by using static variable called arguments. I found that sometimes for some users (cases are not repro) sometimes an exception occured

"WebServiceFailedException the server method 'Foo' returned invalid data. the 'd' property is missing from JSON."

Some searching on google I found that people are serializing the return values using DataContractJsonSerializer class and in js accessing the return value using one of the callback function Example:

function OnRequestComplete(result, userContext, methodName) {

var Person = eval('(' + result + ')'); alert(Person.Forename);

alert(Person.Surname); }

So is the first technique is correct? or what?

P.S: the function on the server is defined on the default.aspx.cs file as follows:

[System.Web.Services.WebMethodAttribute(), System.Web.Script.Services.ScriptMethodAttribute()]
    public static string[] Foo(string s);

from the client side the calling is as follows

PageMethods.Foo("value",OnSuccess);

Also all the user开发者_C百科s have the same browser version (IE8)

I don't know if it's the entire problem, but your first issue is manually serializing the return value. PageMethods and ScriptServices automatically JSON serialize their return values. Nesting two levels of JSON could definitely be throwing a wrench in the framework's client-side deserialization process (which is also happening automatically, before your eval() code).

To return an instance of your Person class, this is all you need:

public static Person GetPerson() {
  Person p = new Person();

  // Populate the Person object here.

  return p;
}

Then, on the client-side you can work with the object's properties as expected:

function OnRequestComplete(result, userContext, methodName) {
  console.log('Person name: ' + result.Forename + ' ' + result.Surname);
}

Alternatively, if you're using jQuery for other tasks and already have it on the page, you don't even need the ScriptManager and MS AJAX to call page methods. You can directly call page methods with jQuery and skip all that overhead.

Without knowing how the request is made and how the server end is coded, my answer may not be accurate.

Where is the WebMethod decorated method in your server side code? If it is an a separate class with the ScriptService attribute, and if JSON is specified while making the request, then the JSON values should have been automatically serialized and dont need to be serialized manually again. With this set up ASP.NET 3.5 wraps the response in a "d" object

Some users getting the exception might be due to the browser that they are using. If you are using jQuery, I'd specify the content type as so in the ajax request body

contentType: "application/json; charset=utf-8",

Hakeem

This is a bit funky. ASP.NET always adds the "d" to all results. So it either should work or not. Here is some background on the "d" issue:
http://encosia.com/2009/06/29/never-worry-about-asp-net-ajaxs-d-again/