chore: add .NET wrapper for SpannerLib

Adds a .NET wrapper and tests for SpannerLib.

Author: olavloite

.github/workflows/spanner-lib-tests.yml

@@ -71,3 +71,56 @@ jobs:
         run: mvn -Djna.debug_load=true test
         working-directory: spannerlib/wrappers/spannerlib-java
         shell: bash
+
+  dotnet-wrapper:
+    strategy:
+      matrix:
+        go-version: [1.25.x]
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - name: Install dotnet
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '9.0.x'
+      - name: Install Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: ${{ matrix.go-version }}
+      - name: Checkout code
+        uses: actions/checkout@v4
+      - name: Build shared library
+        working-directory: spannerlib/shared
+        run: go build -o spannerlib.so -buildmode=c-shared shared_lib.go
+      - name: Copy to .NET wrapper
+        working-directory: spannerlib
+        run: |
+          mkdir -p wrappers/spannerlib-dotnet/spannerlib-dotnet-native/libraries/any
+          cp shared/spannerlib.so wrappers/spannerlib-dotnet/spannerlib-dotnet-native/libraries/any/spannerlib
+        shell: bash
+      - name: Build .NET native library package
+        run: dotnet pack
+        working-directory: spannerlib/wrappers/spannerlib-dotnet/spannerlib-dotnet-native
+        shell: bash
+      - name: Add .NET package source
+        run: |
+          if [ "$RUNNER_OS" == "Windows" ]; then
+            echo ${GITHUB_WORKSPACE}"\spannerlib\wrappers\spannerlib-dotnet\spannerlib-dotnet-native\bin\Release"
+            dotnet nuget add source ${GITHUB_WORKSPACE}"\spannerlib\wrappers\spannerlib-dotnet\spannerlib-dotnet-native\bin\Release" --name local
+          else
+            dotnet nuget add source "$PWD"/bin/Release --name local
+          fi
+        working-directory: spannerlib/wrappers/spannerlib-dotnet/spannerlib-dotnet-native
+        shell: bash
+      - name: Restore dependencies
+        run: dotnet restore
+        working-directory: spannerlib/wrappers/spannerlib-dotnet
+        shell: bash
+      - name: Build
+        run: dotnet build --no-restore
+        working-directory: spannerlib/wrappers/spannerlib-dotnet
+        shell: bash
+      - name: .NET Unit Tests
+        working-directory: spannerlib/wrappers/spannerlib-dotnet/spannerlib-dotnet-tests
+        run: dotnet test --no-build --verbosity normal
+        shell: bash

spannerlib/wrappers/spannerlib-dotnet/.gitignore

@@ -0,0 +1,4 @@
+.idea
+obj
+bin
+*DotSettings.user

spannerlib/wrappers/spannerlib-dotnet/global.json

@@ -0,0 +1,7 @@
+{
+  "sdk": {
+    "version": "9.0.0",
+    "rollForward": "latestMinor",
+    "allowPrerelease": false
+  }
+}

spannerlib/wrappers/spannerlib-dotnet/spannerlib-dotnet-mockserver/MockServerStartup.cs

@@ -0,0 +1,68 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+
+namespace Google.Cloud.SpannerLib.MockServer;
+
+/// <summary>
+/// Helper class for starting an in-memory mock Spanner server that is used for testing.
+/// </summary>
+public class MockServerStartup(MockSpannerService mockSpannerService, MockDatabaseAdminService mockDatabaseAdminService)
+{
+    /// <summary>
+    /// The in-mem Spanner service.
+    /// </summary>
+    private MockSpannerService MockSpannerService { get; } = mockSpannerService;
+
+    /// <summary>
+    /// The in-mem Spanner database admin service for executing DDL operations.
+    /// </summary>
+    private MockDatabaseAdminService MockDatabaseAdminService { get; } = mockDatabaseAdminService;
+
+    /// <summary>
+    /// Configures the services that will be available on this gRPC server.
+    /// This method is called by reflection when the tests are started.
+    /// </summary>
+    /// <param name="services">The services collection where the services should be added</param>
+    public void ConfigureServices(IServiceCollection services)
+    {
+        services.AddGrpc();
+        services.AddSingleton(MockSpannerService);
+        services.AddSingleton(MockDatabaseAdminService);
+    }
+
+    /// <summary>
+    /// Configures the gRPC server. This method is called by reflection when the tests are started.
+    /// </summary>
+    /// <param name="app">The builder for the application that will be hosting the service</param>
+    /// <param name="env">The webhost environment that is hosting the service</param>
+    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
+    {
+        if (env.IsDevelopment())
+        {
+            app.UseDeveloperExceptionPage();
+        }
+
+        app.UseRouting();
+        app.UseEndpoints(endpoints =>
+        {
+            endpoints.MapGrpcService<MockSpannerService>();
+            endpoints.MapGrpcService<MockDatabaseAdminService>();
+        });
+    }
+}