BinaryFormatter Serialization Broken when change form .net 3.5 to .net 4.x

Unity version 2018.3.4f1

The save file is saved by Scripting Runtime Version .NET 3.5. But if switch the Scripting Runtime Version .NET 4.x, the file cannot loaded. It detects the format is not correct.

What I found, using BinaryFormatter Serialization to save data, use Scripting Runtime Version .NET 3.5 can only open .NET 3.5 file, while using .NET 4.x only can open .NET 4.x Serialization file.

When using hex editor to open the two files. There is many different. The main is .net 3.5 file the opening is "Assembly-CSharp", but the .net 4.x file it opening is "FAssembly-CSharp"

I have a main problem, I am using serialization to save player game data, how do I upgrade the runtime to .net 4.x, but able to deserialize the .net 3.5 file?

Unity is deprecated .net 3.5, we need to find the way to read the serialization file when upgrade to .net 4.x

 

No one find it is a problem?

 

It's breaking for me too. Anyone else find a solution to this?

 

If this were me, I'd implement my own save format that doesn't require the BinaryFormatter to be set in stone forever. Release a version of your game which reads the BinaryFormatter version of your save files, and re-saves them in your own format under your control. Then you can release later updates to your game using .net 4.x which will be able to read your save files.

 

This is particularly important in light of:

https://docs.microsoft.com/en-us/dotnet/standard/serialization/binaryformatter-security-guide

tl;dr: Don't use the binary formatter/serializer: it is insecure, it cannot be made secure, and it makes debugging very difficult, plus it actually will NOT prevent people from modifying your save data on their computers.

 

Thanks @Kurt-Dekker,
For sure, Id like to steer clear of it. Although I have existing players where their data is stored in this way (I wish I knew better at the time). As the .NET version compatibility changed with Unity, I'm not even able to migrate the data into a better format.

Is there anyway to salvage the older .NET data?

Thanks again!!

 

I don't know enough about binary formatter to answer this, but at the end of the day it's just bytes on the disk. If you can write yourself an old-style binary save (the way your game used to do), then grab and keep that data, it may be possible to coax a newer version into reading it.

I have had to sunset old savegame formats before, and my upgrade logic is this:

Code (csharp):

1. if (NewFormatSaveGameExists)
2. {
3.   LoadNewFormat();
4.   return;
5. }
6. else
7. {
8.   if (OldFormatSaveGameExists)
9.   {
10.     LoadOldFormat();
11.     SaveNewFormat();
12.     DeleteOldFormat();
13.     return;
14.   }
15.   else
16.   {
17. //// must be a brand-new player!
18.      return;
19.   }
20. }