// *** Service Calling Proxy Class
function serviceProxy(serviceUrl) {
    var _I = this;
    this.serviceUrl = serviceUrl;     // *** Call a wrapped object
    this.invoke = function (method, data, callback, error, bare) {
        // *** Convert input data into JSON - REQUIRES Json2.js        
        var json = JSON.stringify(data);

        // *** The service endpoint URL                
        var url = _I.serviceUrl + method;

        $.ajax({
            url: url,
            data: json,
            type: "POST",
            processData: false,
            contentType: "application/json",
            timeout: 10000,
            dataType: "text",  // not "json" we'll parse
            success:
                function (res) {
                    if (!callback) return;
                    // *** Use json library so we can fix up MS AJAX dates
                    var result = JSON.parse(res);                         // *** Bare message IS result
                    
                    if (bare) { callback(result); return; }                         // *** Wrapped message contains top level object node                        
                    //                    alert(result.toString());
                    // *** strip it off
                    for (var property in result) {

                        callback(result[property]);
                        break;
                    }
                },
            error:
                function (xhr) {
                    if (!error) return;
                    if (xhr.responseText) {
                        var err = JSON.parse(xhr.responseText);

                        if (err)
                            error(err);
                        else
                            error({ Message: "Unknown server error." })
                    } return;
                }
        });
    }
}