I can register a grpc client in DI containter and add an interceptor usin the following code.

builder.Services.AddSingleton<MyInterceptor>();

builder.Services
    .AddGrpcClient<MyService.MyServiceClient>()
    .AddInterceptor<MyInterceptor>();

However, the above solution doesn’t work if there is a parameter in MyInterceptor‘s constructor:

public sealed class MyInterceptor : Interceptor
{
    private readonly int _parameter;

    public MyInterceptor (int parameter)
    {
        _parameter = parameter;
    }
    // more stuff here
}

No I have to use less elegant way of interceptor registration:

builder.Services
        .AddGrpcClient<MyService.MyServiceClient>()
        .AddInterceptor(() => new MyInterceptor(1));

which doesn’t seem very nice to me. Also this solution is not very optimal when I need many interceptors with the same parameter value as it leads to unneccessary memory consumption.

Thus, I decided to use a factory pattern to reuse interceptors with the same parameter value.

public class MyInterceptorPool
{
    private readonly Dictionary<int, MyInterceptor> _pool;

    public MyInterceptorPool()
    {
        _pool = [];
    }

    public MyInterceptor GetOrAddMyInterceptor(int parameter)
    {
        if (_pool.TryGetValue(parameter, out var value))
            return value;

        value = new MyInterceptor(parameter);
        _pool.Add(parameter, value);

        return value;
    }
}

Now I can register my factory as a Singleton and use it to add interceptors like so:

var interceptorPool = services.BuildServiceProvider().GetRequiredService<GrpcDeadlineInterceptorPool>();

builder.Services
            .AddGrpcClient<MyService.MyServiceClient>()
            .AddInterceptor(() => interceptorPool.GetOrAddDeadlineInterceptor(10));

or alternatively

builder.Services
            .AddGrpcClient<MyService.MyServiceClient>()
            .AddInterceptor(sp => sp.GetRequiredService<MyInterceptorPool>().GetOrAddDeadlineInterceptor(10));

While this approach solves the issue, i wonder if there’s a more elegant solution? Perhaps using keyed service registration?

Additionally, I’m uncertain whether using aDictionary in MyInterceptorPool is appropriate? Perhaps I should go with ConcurrentDictionary if ASP .NET Core has some multithreading application configuration.

Any thoughts and comments are highly appreciated.