Hi all.  I'm trying to use the Autocomplete control from the AJAX toolkit in my MVC application.  And I can't seem to get it to work.  Following the example at http://www.asp.net/AJAX/AjaxControlToolkit/Samples/AutoComplete/AutoComplete.aspx, I did the following:

1) Created a new MVC project

2) Added a script manager and autocomplete control inside my aspnetForm

3) Added a method matching the signature defined on the webiste, specifically

[WebMethod]
[ScriptMethod]
public string[] GetCompletionList(string prefixText, int count)
{
    return new string[] { "aaabcdefghijk", "aaabc", "aaabcdefg" 
}

I've attempted every possible combination of ServiceMethod and ServicePath I can think of, putting my GetCompletionList() method both in my controller and in the code behind for the page.  I imagine the code behind is treated differently in MVC as compared to ASP.NET webforms approach, and since requests to the server are /controller/action, that the ServiceMethod and ServicePath properties need to point to something ni the controller, instead of the views code-behind.  But I just can't get the darn thing to work. 
 

Any suggestions? 

Have you included the Ajax JavaScript references on your view? (i.e. all Ajax classes and proxy methods for this script reference)

Yes, the JS is included in the page.

 I've made a little progress, but it's still not quite there.  It turns out your ServicePath needs to be "/controller" (the leading slash is important) and the ServiceMethod is "action". 

Using Firebug in Firefox, I examined the response from the example/tutorial page of a working Autocomplete.  It appears the response is of type 'application/json', and the response content is a simple array, ["aaa", "aab"] etc.

I've mimicked this behavior in my action, by manually setting the resopnse type to 'application/json' and then returning a json formatted string similar to that found in the working example.  However, it still doesn't work.  I get the JSON response just fine (inspected using Firebug), but nothing happens in Firefox.  In IE, I get a javascript error that the "Sys.Net.WebServiceFailedException: The server method 'GetCompletionList' returns invalid data.  The 'd' property is missing from the JSON wrapper"

However, I see no "d" property in the response content of the working example. 

Okay, I got this to work, but here are the tricks involved:

1) ScriptPath = "/controllername" (leading slash important)

2) ScriptMethod = "actionname" 

3) In your action, set the ContentType = "application/json"

4) The response format needs to be as follows: (JSON formatted string)

{ "d" : ["array", "of", "possible", "matches" ] }

Even though, using firebug, the response format from the demo website does not show this "d" property, without it I would get a JS error in IE that the "d" property is undefined.  As far as I can gather, this is done for security reasons, though how this makes the exchange more secure I have no idea. 

5) Don't do RenderView(), instead use Response.Write(), and write out the JSON formatted string from item #4.