csharp/README.md - third_party/protobuf - Git at Google

 This directory contains the C# Protocol Buffers runtime library.

 Usage
 =====

 The easiest way how to use C# protobufs is via the `Google.Protobuf`
 NuGet package. Just add the NuGet package to your VS project.

 You will also want to install the `Google.Protobuf.Tools` NuGet package, which
 contains precompiled version of `protoc.exe` and a copy of well known `.proto`
 files under the package's `tools` directory.

 To generate C# files from your `.proto` files, invoke `protoc` with the
 `--csharp_out` option.

 Supported platforms
 ===================

 The runtime library is built as a class library, supporting targets of:

 - .NET 4.5+ (`net45`)
 - .NET Standard 1.1 and 2.0 (`netstandard1.1` and `netstandard2.0`)
 - .NET 5+ (`net50`)

 You should be able to use Protocol Buffers in Visual Studio 2012 and
 all later versions. This includes all code generated by `protoc`,
 which only uses features from C# 3 and earlier. When compiling generated
 code with old compilers (before C# 7.2) you need to define the
 `GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE` symbol in your project
 so that the generated classes don't implement `IBufferMessage`, which uses
 `ref struct` types.

 Building
 ========

 Open the `src/Google.Protobuf.sln` solution in Visual Studio 2022 or
 later.

 Although *users* of this project are only expected to have Visual
 Studio 2012 or later, *developers* of the library are required to
 have Visual Studio 2022 or later, as the library uses C# 10 features
 in its implementation and runs tests under .NET 6. These features
 have no impact when using the compiled code - they're only relevant
 when building the `Google.Protobuf` assembly.

 Testing
 =======

 The unit tests use [NUnit 3](https://github.com/nunit/nunit). Tests can be
 run using the Visual Studio Test Explorer or `dotnet test`.

 .NET 3.5
 ========

 We don't support .NET 3.5. It *used* to be feasible to build this library
 targeting .NET 3.5, but a number of changes requiring newer runtime/framework
 features have been added over time. While it would no doubt be *possible* to
 rework the current implementation to allow most of the functionality to be built
 in .NET 3.5, this would create an undue maintenance burden.

 History of C# protobufs
 =======================

 This subtree was originally imported from https://github.com/jskeet/protobuf-csharp-port
 and represents the latest development version of C# protobufs, that will now be developed
 and maintained by Google. All the development will be done in open, under this repository
 (https://github.com/protocolbuffers/protobuf).

 The previous project differs from this project in a number of ways:

 - The old code only supported proto2; the new code initially only supported
 proto3 (so no unknown fields, no required/optional distinction, no
 extensions); since then proto2 support has been added
 - The old code was based on immutable message types and builders for
 them
 - The old code did not support maps or `oneof`
 - The old code had its own JSON representation, whereas the new code
 uses the standard protobuf JSON representation
 - The old code had no notion of the "well-known types" which have
 special support in the new code
 - The old project supported some older platforms (such as older
 versions of Silverlight) which are not currently supported in the
 new project
	This directory contains the C# Protocol Buffers runtime library.

	Usage
	=====

	The easiest way how to use C# protobufs is via the `Google.Protobuf`
	NuGet package. Just add the NuGet package to your VS project.

	You will also want to install the `Google.Protobuf.Tools` NuGet package, which
	contains precompiled version of `protoc.exe` and a copy of well known `.proto`
	files under the package's `tools` directory.

	To generate C# files from your `.proto` files, invoke `protoc` with the
	`--csharp_out` option.

	Supported platforms
	===================

	The runtime library is built as a class library, supporting targets of:

	- .NET 4.5+ (`net45`)
	- .NET Standard 1.1 and 2.0 (`netstandard1.1` and `netstandard2.0`)
	- .NET 5+ (`net50`)

	You should be able to use Protocol Buffers in Visual Studio 2012 and
	all later versions. This includes all code generated by `protoc`,
	which only uses features from C# 3 and earlier. When compiling generated
	code with old compilers (before C# 7.2) you need to define the
	`GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE` symbol in your project
	so that the generated classes don't implement `IBufferMessage`, which uses
	`ref struct` types.

	Building
	========

	Open the `src/Google.Protobuf.sln` solution in Visual Studio 2022 or
	later.

	Although users of this project are only expected to have Visual
	Studio 2012 or later, developers of the library are required to
	have Visual Studio 2022 or later, as the library uses C# 10 features
	in its implementation and runs tests under .NET 6. These features
	have no impact when using the compiled code - they're only relevant
	when building the `Google.Protobuf` assembly.

	Testing
	=======

	The unit tests use [NUnit 3](https://github.com/nunit/nunit). Tests can be
	run using the Visual Studio Test Explorer or `dotnet test`.

	.NET 3.5
	========

	We don't support .NET 3.5. It used to be feasible to build this library
	targeting .NET 3.5, but a number of changes requiring newer runtime/framework
	features have been added over time. While it would no doubt be possible to
	rework the current implementation to allow most of the functionality to be built
	in .NET 3.5, this would create an undue maintenance burden.

	History of C# protobufs
	=======================

	This subtree was originally imported from https://github.com/jskeet/protobuf-csharp-port
	and represents the latest development version of C# protobufs, that will now be developed
	and maintained by Google. All the development will be done in open, under this repository
	(https://github.com/protocolbuffers/protobuf).

	The previous project differs from this project in a number of ways:

	- The old code only supported proto2; the new code initially only supported
	proto3 (so no unknown fields, no required/optional distinction, no
	extensions); since then proto2 support has been added
	- The old code was based on immutable message types and builders for
	them
	- The old code did not support maps or `oneof`
	- The old code had its own JSON representation, whereas the new code
	uses the standard protobuf JSON representation
	- The old code had no notion of the "well-known types" which have
	special support in the new code
	- The old project supported some older platforms (such as older
	versions of Silverlight) which are not currently supported in the
	new project