Add gRPC server example with file download

TestGrpc/Files/test.txt

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+Hello world
+This is a test

TestGrpc/Program.cs

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+namespace TestGrpc;
+
+public class Program
+{
+    public static void Main(string[] args)
+    {
+        CreateHostBuilder(args).Build().Run();
+    }
+
+    public static IHostBuilder CreateHostBuilder(string[] args) =>
+        Host.CreateDefaultBuilder(args)
+            .ConfigureWebHostDefaults(webBuilder =>
+            {
+                webBuilder.UseStartup<Startup>();
+            });
+}

TestGrpc/Properties/launchSettings.json

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+{
+  "$schema": "http://json.schemastore.org/launchsettings.json",
+  "profiles": {
+    "http": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": false,
+      "applicationUrl": "http://localhost:5210",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    },
+    "https": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": false,
+      "applicationUrl": "https://localhost:7004;http://localhost:5210",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    }
+  }
+}

TestGrpc/Protos/greet.proto

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+syntax = "proto3";
+
+option csharp_namespace = "TestGrpc";
+
+package greet;
+
+service Greeter {
+  rpc DownloadFile (FileRequest) returns (stream ChunkMsg);
+}
+
+message FileRequest {
+  string FilePath = 1;
+}
+
+message ChunkMsg {
+  string FileName = 1;
+  int64 FileSize = 2;
+  bytes Chunk = 3;
+}

TestGrpc/Services/GreeterService.cs

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+using Google.Protobuf;
+using Grpc.Core;
+using TestGrpc;
+
+namespace TestGrpc.Services;
+
+public class GreeterService : Greeter.GreeterBase
+{
+    private readonly ILogger<GreeterService> _logger;
+    public GreeterService(ILogger<GreeterService> logger)
+    {
+        _logger = logger;
+    }
+
+    public override async Task DownloadFile(FileRequest request, IServerStreamWriter<ChunkMsg> responseStream, ServerCallContext context)
+    {
+        string filePath = request.FilePath;
+
+        if (!File.Exists(filePath))
+        {
+            return;
+        }
+
+        var fileInfo = new FileInfo(filePath);
+
+        var chunk = new ChunkMsg
+        {
+            FileName = Path.GetFileName(filePath),
+            FileSize = fileInfo.Length
+        };
+
+        int fileChunkSize = 64 * 1024;
+
+        byte[] fileByteArray = File.ReadAllBytes(filePath);
+        byte[] fileChunk = new byte[fileChunkSize];
+        int fileOffset = 0;
+
+        while (fileOffset < fileByteArray.Length && !context.CancellationToken.IsCancellationRequested)
+        {
+            int length = Math.Min(fileChunkSize, fileByteArray.Length - fileOffset);
+            Buffer.BlockCopy(fileByteArray, fileOffset, fileChunk, 0, length);
+            fileOffset += length;
+            ByteString byteString = ByteString.CopyFrom(fileChunk);
+
+            chunk.Chunk = byteString;
+            await responseStream.WriteAsync(chunk).ConfigureAwait(false);
+        }
+    }
+}

TestGrpc/Startup.cs

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+using TestGrpc.Services;
+
+namespace TestGrpc;
+
+public class Startup
+{
+    public void ConfigureServices(IServiceCollection services)
+    {
+        services.AddGrpc(o => o.EnableDetailedErrors = true);
+    }
+
+    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
+    {
+        if (env.IsDevelopment())
+        {
+            app.UseDeveloperExceptionPage();
+        }
+
+        app.UseRouting();
+
+        app.UseEndpoints(endpoints =>
+        {
+            endpoints.MapGrpcService<GreeterService>();
+        });
+    }
+}

TestGrpc/TestGrpc.csproj

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+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Protobuf Include="Protos\greet.proto" GrpcServices="Both" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <None Include="Files/test.txt" CopyToOutputDirectory="PreserveNewest" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="CsvHelper" Version="33.0.1" />
+    <PackageReference Include="Grpc.AspNetCore" Version="2.66.0" />
+  </ItemGroup>
+
+</Project>

TestGrpc/appsettings.Development.json

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+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  }
+}

TestGrpc/appsettings.json

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+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*",
+  "Kestrel": {
+    "EndpointDefaults": {
+      "Protocols": "Http2"
+    }
+  }
+}