Read files generated by obsolete BinaryFormatter

[panxn]

Perhaps it's not a good issue, I just need some suggestions.

According to BinaryFormatter Obsoletion Strategy, using BinaryFormatter is error in .NET8, and totally removed in .NET9.

Our product is preparing for it, we plan to replace BinaryFormatter with Json/Xml, but the difficulty is backward compatibility, how to read old file format in new product.

Is there anyway else (except BinaryFormatter) to read/parse files generated by BinaryFormatter? I guess BinaryFormatter saves type info and data members into files, so is it possible to dump all these information into json structure?

Currently I'm trying to create a Migrator.exe that stays in fixed old .NET version (maybe .NET framework) so that BinaryFormatter can keep alive for longer time, however the dependency assemblies are not available, so I create a SerializationBinder to return fake types. I have to say this way is too difficult. That's why I want to ask here to look for a better way.

[teo-tsirpanis]

Item 4 in #29976 seems to be what you need. @GrabYourPitchforks any news on the safe BinaryFormatter deserializer?

[ghost]

Tagging subscribers to this area: @dotnet/area-system-runtime
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Perhaps it's not a good issue, I just need some suggestions.

According to BinaryFormatter Obsoletion Strategy, using BinaryFormatter is error in .NET8, and totally removed in .NET9.

Our product is preparing for it, we plan to replace BinaryFormatter with Json/Xml, but the difficulty is backward compatibility, how to read old file format in new product.

Is there anyway else (except BinaryFormatter) to read/parse files generated by BinaryFormatter? I guess BinaryFormatter saves type info and data members into files, so is it possible to dump all these information into json structure?

Currently I'm trying to create a Migrator.exe that stays in fixed old .NET version (maybe .NET framework) so that BinaryFormatter can keep alive for longer time, however the dependency assemblies are not available, so I create a SerializationBinder to return fake types. I have to say this way is too difficult. That's why I want to ask here to look for a better way.

Author:	panxn
Assignees:	-
Labels:	area-System.Runtime, untriaged
Milestone:	-

[JeremyKuhne]

@panxn in WinForms I created BinaryFormattedObject for manual parsing of existing data. You're welcome to copy it under the MIT license. It can also serialize as well. The only record type it doesn't handle is multidimensional/jagged arrays, didn't need to do that yet so I haven't written it. :)

[GrabYourPitchforks]

@teo-tsirpanis An officially supported package is indeed being discussed, but development of such a package hasn't been resourced. I don't really have any progress on it to share at this time.

If you wanted to take the WinForms code you're totally free to do so. However, it has not been threat modeled or security reviewed for any scenarios outside of WinForms-specific scenarios. You would need to perform your own analysis of it in the context of your own application.

[rickbrew]

This is also critical for Paint.NET -- it'd be nice to have, say, a nuget package that provides BinaryFormatter and all the serialization logic, but requires me to provide surrogate serializers for every type I need to handle (even if that means things like string and T[], I'll do it!). For both serialization and deserialization. Otherwise I can't move forward to whatever version of .NET eventually removes BinaryFormatter (8? 9?), as all .PDN image files (the native multi-layered Paint.NET image format) would become instantly unusable.

I'm planning on revving the .PDN format such that it won't rely on BF at all, and this is the way forward for me anyway so I can actually add new functionality (new layer types, blend modes, etc.), but I still need to support the legacy format that's been used for 20 years by lots and lots of folks.

[JeremyKuhne]

@rickbrew I'm curious whether or not the BinaryFormattedObject mentioned above has the functionality you require. It's effectively a DOM for the NRBF format.

[panxn]

Hi @JeremyKuhne thanks for your advice. We have considered copy .NET code, it should work, just hard to maintenance for us.
Our team has started the plan to convert BF format to JSON via a standalone .NET framework app so that BF keeps available as long as .NET framework is under support.

[rickbrew]

@rickbrew I'm curious whether or not the BinaryFormattedObject mentioned above has the functionality you require. It's effectively a DOM for the NRBF format.

It might work, but I need deserialization and serialization. Otherwise I will not be able to support both the old and new file format versions simultaneously, which could make things quite difficult for some end-users. For example: several people working on project(s), sharing and collaborating on files, but not all of them have the new version of my app. Person 1 saves some images in the new format, but then Person 2 can't load the images at all because they haven't installed the new app version. Maybe they can't because they're in an office and their IT department hasn't deployed the new version, and maybe won't for some time. If I can still use BinaryFormatter and support the old file format version, then Person 1 can at least File -> Save As -> and choose "Legacy .PDN Format" in the file type dropdown.

[tannergooding]

@GrabYourPitchforks does this need to stay open to track the areas being investigated you mentioned or can it be closed?

[GrabYourPitchforks]

@tannergooding this is already being tracked by internal work items. Feel free to keep this open or close it depending on your own needs. I personally don't need this item to remain open.

[jkotas]

API proposal: #102014