Reading data with DataContract gives SerializationException when loading older version

I am trying to use DataContract to save and load my runtime user data, however it does not appear to be working in Unity as specified by the Microsoft documentation

https://docs.microsoft.com/en-us/dotnet/framework/wcf/feature-details/data-contract-versioning

According to the docs, I should be able to change the name of a member and map it using DataMember attribute. However with Unity I get a serialization error when trying to load an older save file.

   System.Runtime.Serialization.SerializationException : Field "Phone" not found in class Person

Am I doing something wrong or is this a known issue with Unity. I am using unity 2017.1.0f3 on Windows 10.

thanks!

Here are the steps to reproduce:
1. create class

Code (CSharp):

1.  
2. using UnityEngine;
3. using System.Runtime.Serialization;
4.  
5. [System.Serializable]
6. [DataContract]
7. public class Person
8. {
9.    [DataMember]
10.    public string Phone;
11. }
12.  

2. save data to disk with

BinaryFormatter.Serialize

3. load data from disk with

BinaryFormatter.Deserialize

- no errors
4. modify class - change "Phone" to "Telephone"

Code (CSharp):

1. using UnityEngine;
2. using System.Runtime.Serialization;
3.  
4. [System.Serializable]
5. [DataContract]
6. public class Person
7. {
8.    //rename Phone to Telephone
9.    [DataMember(Name = "Phone")]
10.    public string Telephone;
11. }
12.  

5. load data from disk with

BinaryFormatter.Deserialize

- get error

  System.Runtime.Serialization.SerializationException : Field "Phone" not found in class Person

---

at System.Runtime.Serialization.Formatters.Binary.ObjectReader.ReadTypeMetadata (System.IO.BinaryReader reader, Boolean isRuntimeObject, Boolean hasTypeInfo) [0x00216] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/ObjectReader.cs:691

  at System.Runtime.Serialization.Formatters.Binary.ObjectReader.ReadObjectInstance (System.IO.BinaryReader reader, Boolean isRuntimeObject, Boolean hasTypeInfo, System.Int64& objectId, System.Object& value, System.Runtime.Serialization.SerializationInfo& info) [0x0000a] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/ObjectReader.cs:269

  at System.Runtime.Serialization.Formatters.Binary.ObjectReader.ReadObject (BinaryElement element, System.IO.BinaryReader reader, System.Int64& objectId, System.Object& value, System.Runtime.Serialization.SerializationInfo& info) [0x0009d] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/ObjectReader.cs:195

  at System.Runtime.Serialization.Formatters.Binary.ObjectReader.ReadObject (BinaryElement element, System.IO.BinaryReader reader, System.Int64& objectId, System.Object& value, System.Runtime.Serialization.SerializationInfo& info) [0x00105] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/ObjectReader.cs:223

  at System.Runtime.Serialization.Formatters.Binary.ObjectReader.ReadNextObject (BinaryElement element, System.IO.BinaryReader reader) [0x00020] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/ObjectReader.cs:130

  at System.Runtime.Serialization.Formatters.Binary.ObjectReader.ReadObjectGraph (BinaryElement elem, System.IO.BinaryReader reader, Boolean readHeaders, System.Object& result, System.Runtime.Remoting.Messaging.Header[]& headers) [0x00004] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/ObjectReader.cs:104

  at System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.NoCheckDeserialize (System.IO.Stream serializationStream, System.Runtime.Remoting.Messaging.HeaderHandler handler) [0x00078] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/BinaryFormatter.cs:179

  at System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Deserialize (System.IO.Stream serializationStream) [0x00000] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/BinaryFormatter.cs:136

  at Persist.Load (System.String path) [0x0003c] in C:\Users\quyrean\Documents\unity projects\tutorial-heart-ui-test\Assets\contract test\Persist.cs:33

  at PersonTest+PersistTest.test_1_load () [0x00007] in C:\Users\quyrean\Documents\unity projects\tutorial-heart-ui-test\Assets\Editor\PersonTest.cs:22

  at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (object,object[],System.Exception&)

  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x000d0] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222

---

Reading file c:/tmp/fred.bin

fyi: code to save and load

Code (CSharp):

1. using UnityEngine;
2. using System.Runtime.Serialization;
3. using System.Runtime.Serialization.Formatters.Binary;
4. using System.IO;
5.  
6. public static class Persist {
7.  
8.    //save and restore character data for pc's
9.    //default path C:\Users\quyrean\AppData\LocalLow\BohnStar\NTrek1\info1.bin
10.    public static void Save(string path, Person data) {
11.        Debug.Log ("Saving to " + path);
12.        //binary
13.        IFormatter formatter = new BinaryFormatter();
14.        Stream stream2 = new FileStream(path + ".bin",
15.            FileMode.Create,
16.            FileAccess.Write, FileShare.None);
17.        formatter.Serialize(stream2, data);
18.        stream2.Close();
19.    }
20.  
21.    public static Person Load(string path)
22.    {
23.        path += ".bin";
24.        Person answer;
25.  
26.        if (File.Exists (path)) {
27.            Debug.Log ("Reading file " + path);
28.            IFormatter formatter = new BinaryFormatter ();
29.            Stream stream = new FileStream (path,
30.                FileMode.Open,
31.                FileAccess.Read,
32.                FileShare.Read);
33.            answer = (Person)formatter.Deserialize (stream);
34.            stream.Close ();
35.            return answer;
36.  
37.        } else {
38.            Debug.Log ("File does not exist " + path);
39.        }
40.  
41.        return null;
42.    }
43. }
44.  

 

Well you are trying to read a file that has the phone value and map it on an object with that value missing because of renaming to telephone. You need to load it, save it as a new value, delete the phone value and seralize it again afaik.

 

Yes, that is what I am trying to do. That is why I used the attribute:

[DataMember(Name = "Phone")]

According to the microsoft docs, this should be backwards compatible.

https://docs.microsoft.com/en-us/dotnet/framework/wcf/feature-details/data-contract-versioning