access variables inside asp.net-core grpc service class from different thread

Question

I've generated c# code from a .proto-file for grpc communication. My proto file contains a service:

syntax = "proto3";

option csharp_namespace = "GrpcEmployee";

service ClientFileStreamService {

  rpc ReceiveFileChunks(stream FileChunks) returns (FileResponse);
}

message FileChunks {
  bytes chunk = 1;
  int64 timestamp = 2;
  int64 token = 3;
  int32 totalbytes=4;
  int32 sentbytes=5;
}

message FileResponse {
  int64 token = 1;
  uint32 receivedbytes=2;
}

and I've created the following C# code to be used on the grpc server side:

    public class ClientFileStreamServe : ClientFileStreamService.ClientFileStreamServiceBase
    {
        private readonly ILogger<ClientFileStreamServe> _logger;

        public ClientFileStreamServe(ILogger<ClientFileStreamServe> logger)
        {
            _logger = logger;
        }

        public override async Task<FileResponse> ReceiveFileChunks(IAsyncStreamReader<FileChunks> request, ServerCallContext context)
        {
            System.IO.MemoryStream total_message_stream = new System.IO.MemoryStream();
            
            long token = 0;

            await foreach (var message in request.ReadAllAsync())
            {
                var bytearraychunk = request.Current.Chunk.ToByteArray();
                total_message_stream.Write(bytearraychunk, 0, bytearraychunk.Length);
                token = request.Current.Token;
            }
            var full_file = total_message_stream.ToArray(); // I WANT TO ACCESS THIS FROM A DIFFERENT THREAD
            _logger.LogInformation("Received {} bytes, last token {}", full_file.Length, token);
            return new FileResponse { Receivedbytes = full_file.Length, Token = token };
        }
    }

In the third last code line there is a variable full_file which I would like to access from a different thread (probably via a Getter). Preferable I would just get a reference to the instance of the class ClientFileStreamServe and go from there, but here I struggle. I started my tests off with the example from https://docs.microsoft.com/en-us/aspnet/core/grpc/?view=aspnetcore-6.0 where ASP.NET core is used.

There is a file startup.cs which registers my class CLientFileStreamServe as an endpoint like this:

endpoints.MapGrpcService<GrpcEmployee.ClientFileStreamServe>();

Since I don't have an instance of ClientFileStreamServe here, I can't access it. Also it seems that ClientFileStreamServe is instantiated every time a http-call is made to the server.

How can I access the variable full_file or how can I pass information to a different thread in my program? I had a look at named pipes, but is this the only way?