Serialization exception using C# -

i new c# , trying write information file. got program running when have car class in same .cs file, when remove class .cs file in project, runtime error of

"serializationexception unhandled: objectmanager found invalid number of fixups. indicates problem in formatter".

below code car class included. when move class own car.cs file error starts getting thrown.

namespace consoleapplication2 {   class program   {       [serializable()]      public class car      {          public string make { get; set; }          public string model { get; set; }          public int year { get; set; }           public car(string make, string model, int year)         {              make = make;              model = model;              year = year;         }      }     /// <summary>     /// deserializes list of cars , returns list user     /// </summary>     /// <returns>returns deserialized car list</returns>     public list<car> readlist()     {         //create local list hold data         list<car> carlist = new list<car>();          try         {             using (stream stream = file.open("data.bin", filemode.open))             {                 binaryformatter bin = new binaryformatter();                  //point carlist deserialized stream                 carlist = (list<car>)bin.deserialize(stream);              }         }         catch (ioexception)         {         }          return carlist;      } 

when data.bin first created class type stored along data. if change class's namespace, formatter not able find class stored.