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+This directory contains the C# Protocol Buffers runtime library.
+
+Status: Beta - ready for external testing
+=========================================
+
+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 portable class library, supporting:
+
+- .NET 4.5
+- Windows 8
+- Windows Phone Silverlight 8
+- Windows Phone 8.1
+- .NET Core
+
+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.
+
+Building
+========
+
+Open the `src/Google.Protobuf.sln` solution in Visual Studio 2015 or
+later. You should be able to run the NUnit test from Test Explorer
+(you might need to install NUnit Visual Studio add-in).
+
+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 2015 or later, as the library uses C# 6 features
+in its implementation. These features have no impact when using the
+compiled code - they're only relevant when building the
+`Google.Protobuf` assembly.
+
+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/google/protobuf).
+
+The previous project differs from this project in a number of ways:
+
+- The old code only supported proto2; the new code only supports
+proto3 (so no unknown fields, no required/optional distinction, no
+extensions)
+- 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