protobuf-net is a contract based serializer for .NET code, that happens to write data in the "protocol buffers" serialization format engineered by Google. The API, however, is very different to Google's, and follows typical .NET patterns (it is broadly comparable, in usage, to XmlSerializer, DataContractSerializer, etc). It should work for most .NET languages that write standard types and can use attributes.

v3 is here!

Change history and pending changes are here.

• .NET Framework 4.6.1+
• .NET Standard 2.0+

All stable and some pre-release packages are available on NuGet. CI Builds are available via MyGet (feed URL: https://www.myget.org/F/protobuf-net/api/v3/index.json ).

You can use the following command in the Package Manager Console:

Install-Package protobuf-net

Package	NuGet Stable	NuGet Pre-release	Downloads	MyGet
protobuf-net

[ProtoContract]
class Person {
    [ProtoMember(1)]
    public int Id {get;set;}
    [ProtoMember(2)]
    public string Name {get;set;}
    [ProtoMember(3)]
    public Address Address {get;set;}
}
[ProtoContract]
class Address {
    [ProtoMember(1)]
    public string Line1 {get;set;}
    [ProtoMember(2)]
    public string Line2 {get;set;}
}

Note that unlike XmlSerializer, the member-names are not encoded in the data - instead, you must pick an integer to identify each member. Additionally, to show intent it is necessary to show that we intend this type to be serialized (i.e. that it is a data contract).

This writes a 32 byte file to "person.bin" :

var person = new Person {
    Id = 12345, Name = "Fred",
    Address = new Address {
        Line1 = "Flat 1",
        Line2 = "The Meadows"
    }
};
using (var file = File.Create("person.bin")) {
    Serializer.Serialize(file, person);
}

This reads the data back from "person.bin" :

Person newPerson;
using (var file = File.OpenRead("person.bin")) {
    newPerson = Serializer.Deserialize<Person>(file);
}

• they must be positive integers (for best portability, they should be <= 536870911 and not in the range 19000-19999)
• they must be unique within a single type but the same numbers can be re-used in sub-types if inheritance is enabled
• the identifiers must not conflict with any inheritance identifiers (discussed later)
• lower numbers take less space - don't start at 100,000,000
• the identifier is important; you can change the member-name, or shift it between a property and a field, but changing the identifier changes the data

Inheritance must be explicitly declared, in a similar way that it must for XmlSerializer and DataContractSerializer. This is done via [ProtoInclude(...)] on each type with known sub-types:

[ProtoContract]
[ProtoInclude(7, typeof(SomeDerivedType))]
class SomeBaseType {...}

[ProtoContract]
class SomeDerivedType {...}

There is no special significance in the 7 above; it is an integer key, just like every [ProtoMember(...)]. It must be unique in terms of SomeBaseType (no other [ProtoInclude(...)] or [ProtoMember(...)] in SomeBaseType can use 7), but does not need to be unique globally.

As an alternative to writing your classes and decorating them, You can generate your types from a .proto schema using protogen; the protogen tool is available as a zip from that location, or as a "global tool" (multi-platform).

In v2+, everything that can be done with attributes can also be configured at runtime via RuntimeTypeModel. The Serializer.* methods are basically just shortcuts to RuntimeTypeModel.Default., so to manipulate the behaviour of Serializer., you must configure RuntimeTypeModel.Default.

I try to be responsive to Stack Overflow questions in the protobuf-net tag, issues logged on GitHub, email, etc. I don't currently offer a paid support channel. If I've helped you, feel free to buy me a coffee or see the "Sponsor" link at the top of the GitHub page.