Using MapPath with WCF Service, Setting aspNetCompatibilityEnabled to true

I'm just starting out using WCF in an application for the first time.  I'm using Visual Studio 2008 sp1 and created an asp.net web site from the standard create project wizard.  I then created a simple AJAX--enabled WCF Service as follows:

I then added some code to the service that looks like the following (using MapPath):

[ServiceContract(Namespace = "")]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class TrackData
{
// Add [WebGet] attribute to use HTTP GET
[OperationContract]
<span class="kwrd">public</span> List&lt;TrackDataList&gt; RetrieveTrackDataByLap(<span class="kwrd">int</span> excerciseId, <span class="kwrd">int</span> lapNumberToShow)

{
    var listTrackData = <span class="kwrd">new</span> List&lt;TrackDataList&gt;();

    <span class="kwrd">string</span> fileName = HttpContext.Current.Server.MapPath(<span class="str">&quot;~/App_Data/sample.tcl&quot;</span>);

    Activity activity = GarminUtils.ConvertTCS(fileName);
I call it with JavaScript as follows:
/// <reference path=“MapLive.aspx” />
/// <reference path=“../VEJS/VeJavaScriptIntellisenseHelper.js” />
function pageLoad() {
TrackData.RetrieveTrackDataByLap(0, 0, OnRetrieveTrackDataByLapComplete);
}
function OnRetrieveTrackDataByLapComplete(TrackDataList) {
alert(<span class="str">'OnRetrieveTrackDataByLapComplete called'</span>);
}

And, I'm surprised to find that I get a JavaScript error saying MapPath is undefined.  So, after a little digging I discover that I need to set aspNetCompatibilityEnabled to true in my web.config as follows:

By default, it is set to false.  Hope this Helps!