function getQuerystring(key, default_) {
    if (default_ == null) default_ = "";
    key = key.replace(/[\[]/, "\\\[").replace(/[\]]/, "\\\]");
    var regex = new RegExp("[\\?&]" + key + "=([^&#]*)");
    var qs = regex.exec(window.location.href);
    if (qs == null)
        return default_;
    else
        return qs[1];
}


var Facebook = new function () {

    this._CheckLogin = function (returnUrl) {
        if (FB) {
            FB.getLoginStatus(function (response) {
                if (response.session) {
                    var uid = response.session["uid"];
                    var access_token = response.session["access_token"];
                    jQuery.ajax({
                        type: "POST",
                        url: "/FBUtils.aspx/UserIDExists",
                        data: "{ uid: '" + uid + "', accesstoken: '" + access_token + "', returnurl: '" + returnUrl + "'}",
                        contentType: "application/json; charset=utf-8",
                        dataType: "json",
                        success: function (data) {
                            var obj = jQuery.parseJSON(data.d);
                            if (obj['result'] == "true") {
                                response.session["isfacebooklogin"] = "true";
                                window.location = obj['returnUrl'];
                            }
                        }
                    });
                } else {
                    // The user has logged out, and the cookie has been cleared
                }
            });
        }
    };
};