Example of consuming gRPC service with Azure API Management

Consume-gRPC-from-Azure-API-Management.cs

using Grpc.Net.Client;
using System.Security.Authentication;

Console.WriteLine("Hello, World!");

var endpointAddress = "https://localhost:8124";
var apiPrefix = "grpc-api";
var subscriptionKey = "<subscription-key>";

GrpcChannel grpcChannel = CreateGrpcChannel(endpointAddress, apiPrefix, subscriptionKey);

var client = new TestService.TestServiceClient(grpcChannel);

// unary
var payload = new Foo { Value = 1000 };
Console.WriteLine($"Sending unary request with payload {payload.Value}");
var unaryRequest = client.UnaryAsync(payload);

Foo unaryResponse = await unaryRequest;
Console.WriteLine($"Received {unaryResponse.Value}.");

Console.WriteLine("Goodbye!");
Console.ReadLine();

static GrpcChannel CreateGrpcChannel(string endpointAddress, string apiPrefix, string subscriptionKey)
{
    Console.WriteLine($"Connecting to {endpointAddress} with API prefix {apiPrefix}.");
    
    // Only required for when not (properly) exposing on HTTPS
    var httpHandler = new SocketsHttpHandler()
    {
        SslOptions = new()
        {
            RemoteCertificateValidationCallback = (_, _, _, _) => true,
            EnabledSslProtocols = SslProtocols.Tls | SslProtocols.Tls11 | SslProtocols.Tls12 | SslProtocols.Tls13,
        }
    };

    // Use a handler given we use an Azure API Management use API prefixes
    // https://learn.microsoft.com/en-us/aspnet/core/grpc/troubleshoot?view=aspnetcore-7.0#calling-grpc-services-hosted-in-a-sub-directory
    var apiPrefixHandler = new ApiPrefixHandler(httpHandler, apiPrefix, subscriptionKey, enableApiInspector: true);

    return GrpcChannel.ForAddress(endpointAddress, new GrpcChannelOptions { HttpHandler = apiPrefixHandler });
}

public class ApiPrefixHandler : DelegatingHandler
{
    readonly bool enableApiInspector;
    readonly string pathPrefix;
    readonly string subscriptionKey;

    public ApiPrefixHandler(HttpMessageHandler innerHandler, string pathPrefix, string subscriptionKey, bool enableApiInspector)
        : base(innerHandler)
    {
        this.pathPrefix = pathPrefix;
        this.subscriptionKey = subscriptionKey;
        this.enableApiInspector = enableApiInspector;
    }

    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        var old = request.RequestUri;

        var url = $"{old.Scheme}://{old.Host}:{old.Port}/{this.pathPrefix}{old.AbsolutePath}";
        request.RequestUri = new Uri(url, UriKind.Absolute);

        request.Headers.TryAddWithoutValidation("Ocp-Apim-Subscription-Key", this.subscriptionKey);

        if (this.enableApiInspector)
        {
            request.Headers.TryAddWithoutValidation("Ocp-Apim-Trace", Boolean.TrueString);
        }

        return base.SendAsync(request, cancellationToken);
    }
}

schema.proto

syntax = "proto3";

service TestService {
    rpc Unary(Foo) returns (Foo);
    rpc ClientStreaming(stream Foo) returns (Foo);
    rpc ServerStreaming(Foo) returns (stream Foo);
    rpc Duplex(stream Foo) returns (stream Foo);
}

message Foo {
    int32 value = 1;
}