jquery如何反序列化json对象

[{"id":"67","name":"TestString"}]

我尝试在下面这样做,但不能成功……

success: function (data,status) {
          $.each(data,function (dt) {

              var mydata = data.d;

              alert(mydata); // returns [{"id":"67","name":"TestString"}]

              $("#txt_speciality").tokenInput("add",mydata.id);
          });
}

这是我创建json对象的方式

[WebMethod]
public static string get_specialities(string ProfessionalID)
{
    Database db = DatabaseFactory.CreateDatabase("Connection String2");
    DbCommand dbCommand;
    dbCommand = db.GetStoredProcCommand("Select_Professionals_Speciality");
    db.AddInParameter(dbCommand,"prof_id",DbType.Int16,Convert.ToInt16(ProfessionalID));
    IDataReader dr = db.ExecuteReader(dbCommand);
    //[{ id: 3,name: "test3" }]
    string return_str="[";
    int i = 0;
    while (dr.Read()) {
        if (i > 0)
            return_str += ",";
        return_str += "{\"id\":\"" + dr["SpecialtyID"].ToString().Trim() + "\",\"name\":\"" + dr["SpecialtyName"].ToString().Trim() + "\"}";
        i++;
    }
    return_str += "]";
    return return_str;
}