Add dotnet restore steps to grpc/c# v1.65.1 and pb/c# v27.0 (#1436)

Based on #1429.

plugins/grpc/csharp/v1.65.1/.dockerignore

@@ -1,2 +1,3 @@
 *
 !Dockerfile
+!build.csproj

plugins/grpc/csharp/v1.65.1/Dockerfile

@@ -17,10 +17,16 @@ WORKDIR /build/grpc
 RUN bazel build //src/compiler:grpc_plugin_support
 RUN bazel build //src/compiler:grpc_csharp_plugin.stripped
 
+FROM mcr.microsoft.com/dotnet/sdk:8.0.401-bookworm-slim@sha256:8c6beed050a602970c3d275756ed3c19065e42ce6ca0809f5a6fcbf5d36fd305 AS dotnetrestore
+WORKDIR /build
+COPY --link ./build.csproj /build/build.csproj
+RUN mkdir /nuget && dotnet restore --packages /nuget
+
 FROM gcr.io/distroless/cc-debian12:latest@sha256:3b75fdd33932d16e53a461277becf57c4f815c6cee5f6bc8f52457c095e004c8 AS base
 
 FROM scratch
 COPY --link --from=base / /
+COPY --link --from=dotnetrestore /nuget /nuget
 COPY --link --from=build --chmod=0755 /build/grpc/bazel-bin/src/compiler/grpc_csharp_plugin .
 USER nobody
 ENTRYPOINT ["/grpc_csharp_plugin"]

plugins/grpc/csharp/v1.65.1/buf.plugin.yaml

@@ -18,4 +18,3 @@ registry:
     deps:
       - name: Grpc.Net.Common
         version: 2.63.0
-

plugins/grpc/csharp/v1.65.1/build.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>netstandard2.0</TargetFramework>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="Grpc.Net.Common" Version="2.63.0" />
+    <PackageReference Include="Google.Protobuf" Version="3.26.1" />
+  </ItemGroup>
+</Project>

plugins/protocolbuffers/csharp/v27.0/.dockerignore

@@ -2,3 +2,4 @@
 !BUILD
 !csharp.cc
 !Dockerfile
+!build.csproj

plugins/protocolbuffers/csharp/v27.0/Dockerfile

@@ -18,10 +18,16 @@ RUN bazel build '//:protoc_lib'
 COPY --link BUILD csharp.cc plugins/
 RUN bazel build '//plugins:protoc-gen-csharp.stripped'
 
+FROM mcr.microsoft.com/dotnet/sdk:8.0.401-bookworm-slim@sha256:8c6beed050a602970c3d275756ed3c19065e42ce6ca0809f5a6fcbf5d36fd305 AS dotnetrestore
+WORKDIR /build
+COPY --link ./build.csproj /build/build.csproj
+RUN mkdir /nuget && dotnet restore --packages /nuget
+
 FROM gcr.io/distroless/cc-debian12:latest@sha256:e1065a1d58800a7294f74e67c32ec4146d09d6cbe471c1fa7ed456b2d2bf06e0 AS base
 
 FROM scratch
 COPY --from=base --link / /
+COPY --link --from=dotnetrestore /nuget /nuget
 COPY --from=build --link --chmod=0755 /build/bazel-bin/plugins/protoc-gen-csharp .
 USER nobody
 ENTRYPOINT ["/protoc-gen-csharp"]

plugins/protocolbuffers/csharp/v27.0/build.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>netstandard1.1</TargetFramework>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="Google.Protobuf" Version="3.27.0" />
+  </ItemGroup>
+</Project>