Angular http.get returns Cannot read property 'success' of undefined

For testing purposes, I am trying to make changes to my service calls in Angular. In the sample below, the commented out code works correctly but the uncommented code returns a TypeError: Cannot read property 'success' of undefined.

app.service("waiverService", [
    "$http", function ($http) {
        var _this = this;
        this.get = function (param1, param2) {
            //return $http({
            //    method: "GET",
            //    url: "api/GetInfo/Get/" + param1 + "/" + param2
            //})
            //    .success(function (data) {
            //        _this.result = data;
            //        return data;
            //    })
            //    .error(function () {
            //        return "Error";
            //    })
            //;

            return $http.get("api/GetInfo/Get/" + param1 + "/" + param2)
                .success(function (data) {
                    _this.result = data;
                    return data;
                })
                .error(function() {
                    return "Error";
                });
       };
}]);

What am I missing that causes this error?