enable building nuget package

csharp/build_packages.bat

diff --git a/csharp/build_packages.bat b/csharp/build_packages.bat
new file mode 100644
index 0000000..315c150
--- /dev/null
+++ b/csharp/build_packages.bat
@@ -0,0 +1,13 @@
+@rem Builds Google.Protobuf NuGet packages
+
+@rem Adjust the location of nuget.exe
+set NUGET=C:\nuget\nuget.exe
+
+@rem Build src/ProtocolBuffers.sln solution in Release configuration first.
+%NUGET% pack src\ProtocolBuffers\Google.Protobuf.nuspec -Symbols || goto :error
+
+goto :EOF
+
+:error
+echo Failed!
+exit /b %errorlevel%