FireLance/FireLance/FireLanceGFS.cs

using MongoDB.Bson;
using MongoDB.Driver;
using MongoDB.Driver.GridFS;
using System.IO;
using System.Runtime.CompilerServices;
using System.Threading.Tasks;

namespace Firelance
{
    public class FirelanceGFS : IFlcMongoDBConnecton
    {
        private GridFSBucket gridFSBucket;
        public void SetDatabaseInstance(IMongoDatabase db)
        {
            gridFSBucket = new GridFSBucket(db, new GridFSBucketOptions
            {
                BucketName = Collections.SaveGamesBucket
            });
        }

        public async Task<string> UploadFile(string fileName, string location)
        {
            ObjectId fileId;
            using (var fs = new FileStream(location, FileMode.Open))
            {
                fileId = await gridFSBucket.UploadFromStreamAsync(fileName, fs);
            }

            return fileId.ToString();
        }

        public async Task<bool> DownloadFile(ObjectId id, string saveLocation)
        {
            using (var fs = new FileStream(saveLocation, FileMode.Create))
            {
                await gridFSBucket.DownloadToStreamAsync(id, fs);
            }

            return VerifyDownloadedFile(saveLocation);
        }

        public async Task DeleteFile(ObjectId id) { await gridFSBucket.DeleteAsync(id); }

        private bool VerifyDownloadedFile(string path) { return File.Exists(path); }
    }
}