Renci.SshNet.SftpClient.InternalSynchronizeDirectories C# (CSharp) Method

        private IEnumerable<FileInfo> InternalSynchronizeDirectories(string sourcePath, string destinationPath, string searchPattern, SftpSynchronizeDirectoriesAsyncResult asynchResult)
        {
            if (!Directory.Exists(sourcePath))
                throw new FileNotFoundException(string.Format("Source directory not found: {0}", sourcePath));

            var uploadedFiles = new List<FileInfo>();

            var sourceDirectory = new DirectoryInfo(sourcePath);

            var sourceFiles = FileSystemAbstraction.EnumerateFiles(sourceDirectory, searchPattern).ToList();
            if (sourceFiles.Count == 0)
                return uploadedFiles;

            #region Existing Files at The Destination

            var destFiles = InternalListDirectory(destinationPath, null);
            var destDict = new Dictionary<string, SftpFile>();
            foreach (var destFile in destFiles)
            {
                if (destFile.IsDirectory)
                    continue;
                destDict.Add(destFile.Name, destFile);
            }

            #endregion

            #region Upload the difference

            const Flags uploadFlag = Flags.Write | Flags.Truncate | Flags.CreateNewOrOpen;
            foreach (var localFile in sourceFiles)
            {
                var isDifferent = !destDict.ContainsKey(localFile.Name);

                if (!isDifferent)
                {
                    var temp = destDict[localFile.Name];
                    //  TODO:   Use md5 to detect a difference
                    //ltang: File exists at the destination => Using filesize to detect the difference
                    isDifferent = localFile.Length != temp.Length;
                }

                if (isDifferent)
                {
                    var remoteFileName = string.Format(CultureInfo.InvariantCulture, @"{0}/{1}", destinationPath, localFile.Name);
                    try
                    {
                        using (var file = File.OpenRead(localFile.FullName))
                        {
                            InternalUploadFile(file, remoteFileName, uploadFlag, null, null);
                        }

                        uploadedFiles.Add(localFile);

                        if (asynchResult != null)
                        {
                            asynchResult.Update(uploadedFiles.Count);
                        }
                    }
                    catch (Exception ex)
                    {
                        throw new Exception(string.Format("Failed to upload {0} to {1}", localFile.FullName, remoteFileName), ex);
                    }
                }
            }

            #endregion

            return uploadedFiles;
        }