angularjs - SyntaxError: Unexpected token when request return from server

Question

I'm using angular for my frontend and C# asmx service to correspond with the DB.

I have service for authenticating a user's password. The C# service returns the password and the angular service validates is.

C# service:

[WebMethod]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public void Auth(string username)
{
    string password = "";
    using (SqlConnection con = new SqlConnection(GetConnectionString()))
    {
        SqlCommand cmd = new SqlCommand("Select PASSWORD from users where USERNAME = '" + username + "'", con);

        //Open Connection
        con.Open();

        //To Read From SQL Server
        SqlDataReader dr = cmd.ExecuteReader();

        while (dr.Read())
        {
            password = dr["PASSWORD"].ToString();
        }

        //Close Connection
        dr.Close();
        con.Close();
        this.Context.Response.ContentType = "application/json; charset=utf-8";
        this.Context.Response.Write(password);

    }
}

angular service:

service.Login = function (username, password, callback) {
        var q = $q.defer;
        $http({
            url: 'services/ShiftLogService.asmx/Auth',
            dataType: "json",
            method: "POST",
            data: { username: username }
        }).success(function (data) {
            console.log(data);
        }).error(function (data) {
           // q.reject();
        });
        return q.promise;

    };

The C# service acts fine. The response is good. I know this is not best practice or secure, leave it aside please.

The angular service throws

SyntaxError: Unexpected token l
at Object.parse (native)
at uc (http://localhost:15380/bower_components/angular/angular.min.js:17:6)
at ac (http://localhost:15380/bower_components/angular/angular.min.js:90:253)
at http://localhost:15380/bower_components/angular/angular.min.js:91:164
at q (http://localhost:15380/bower_components/angular/angular.min.js:7:355)
at ed (http://localhost:15380/bower_components/angular/angular.min.js:91:146)
at c (http://localhost:15380/bower_components/angular/angular.min.js:92:403)
at http://localhost:15380/bower_components/angular/angular.min.js:128:305
at m.$eval (http://localhost:15380/bower_components/angular/angular.min.js:142:467)
at m.$digest (http://localhost:15380/bower_components/angular/angular.min.js:140:47)(anonymous function) @ angular.js:13363(anonymous function) @ angular.js:10162(anonymous function) @ angular.js:15621m.$eval @ angular.js:17059m.$digest @ angular.js:16771m.$apply @ angular.js:17121g @ angular.js:11298x @ angular.js:11561v.onload @ angular.js:11624

Can you help me with this please? Thanks.

Could you open the network tab and check your response, it looks like the response isn't valid JSON — Martijn Welker
– Martijn Welker, Commented Mar 29, 2016 at 8:33
Why is your method void? Would it not be better to return a string, and JSON serialise the return data? I thought that a web service would return the data using return statement, rather than writing to the response stream. Maybe that doesn't matter, but I think you still should JSON serialise the data, as a JSON string, and write that to the response stream e.g. { password: "password" } — Jason Evans
– Jason Evans, Commented Mar 29, 2016 at 8:34

Davit Tvildiani · Accepted Answer · 2016-03-29 09:20:26Z

1

This is because you are returning string and not valid json.

public class PassWordClass{
    public string Password {set; get;}
}

[WebMethod]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public PassWordClass Auth(string username)
{
    string password = "";
    using (SqlConnection con = new SqlConnection(GetConnectionString()))
    {
        SqlCommand cmd = new SqlCommand("Select PASSWORD from users where USERNAME = '" + username + "'", con);

        //Open Connection
        con.Open();

        //To Read From SQL Server
        SqlDataReader dr = cmd.ExecuteReader();

        while (dr.Read())
        {
            var pass = new PassWordClass();
            pass.Password = dr["PASSWORD"].ToString();
            return pass;
        }
    }
}

this is correct way of transform requested json:

 $http({
            url: 'services/ShiftLogService.asmx/Auth',
            responseType : "json", //<-- change like that
            method: "POST",
            data: { username: username }
        })

edited Mar 29, 2016 at 9:20

answered Mar 29, 2016 at 8:33

Davit Tvildiani

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1 Comment

Saar Kuriel Over a year ago

Better now, at least the syntax error is gone. But, now the data returned is always null. If I test the C# service alone, it does return the object as expected, I can even see when debugging in VS. Why is the data null?

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