Formatting json data to group by items

I have angular application where I am trying to get json in particular format. I am pulling data from db and database has table data as

Country State 
China   chungchong
India   hyderabad 
USA     florida
India   delhi
USA     redmond

I am trying to get json with list of countries and each country having cities in an array.

angular.module('app')
.factory('CountyStatesService', [
    '$resource', function($resource) {
        return $resource('/api/GetCountryStates/');
    }
])

GetCountryStates() method is a csharp method which just returns list of all data from the table.

I am trying to get json sorted/grouped by in the below format

 data: [
               { text: "China", items: [
        {text: "chungchong"}
        ] },
               {
                   text: "India", items: [
                   { text: "Hyderabad" },
                   { text: "Delhi" }
                   ]
               },
               {
                   text: "USA", items: [
                   { text: "Florida" },
                   { text: "Redmond" }
                   ]
               }
            ]

But I am getting json with out grouping. How can I achieve json format as expected.

C# code

[HttpGet]
    public IEnumerable<CountrieStatesClass> GetCountryState()
    {
        return GetStructuredJson();
    }

public IEnumerable<CountrieStatesClass> GetStructuredJson()
    {
        List<CountrieStatesClass> locations = new List<CountrieStatesClass>();

        using (SqlConnection connection = new SqlConnection(MyConnectionString))
        {
            connection.Open();
            var command = connection.CreateCommand();
            command.CommandText = "select * from tblCountryStateDetails";
            using (var reader = command.ExecuteReader())
            {
                while (reader.Read())
                {
                    CountrieStatesClass location = new CountrieStatesClass
                    {
                        CountryName = (string)reader["CountryName"],
            StateName=(string)reader["StateName"]
                    };
                    locations.Add(location);
                }
            }
            return locations;
        }
    }

via Chebli Mohamed