Programming language: C#
License: MIT License
Tags: Tools    
Latest version: v2.0.0

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:rocket: Fast and reliable multipart downloader with .Net Core 3.1+ supporting :rocket:

Downloader is a modern, fluent, asynchronous, testable and portable library for .NET. This is a multipart downloader with asynchronous progress events. This library can added in your .Net Core v3.1 and later or .Net Framework v4.5 or later projects.

Downloader is compatible with .NET Standard 2.0 and above, running on Windows, Linux, and macOS, in full .NET Framework or .NET Core.

Sample Console Application


How to use

Get it on NuGet:

PM> Install-Package Downloader

Or via the .NET Core command line interface:

dotnet add package Downloader

Create your custom configuration:

var downloadOpt = new DownloadConfiguration()
    BufferBlockSize = 10240, // usually, hosts support max to 8000 bytes, default values is 8000
    ChunkCount = 8, // file parts to download, default value is 1
    MaximumBytesPerSecond = 1024 * 1024, // download speed limited to 1MB/s, default values is zero or unlimited
    MaxTryAgainOnFailover = int.MaxValue, // the maximum number of times to fail
    OnTheFlyDownload = false, // caching in-memory or not? default values is true
    ParallelDownload = true, // download parts of file as parallel or not. Default value is false
    TempDirectory = "C:\\temp", // Set the temp path for buffering chunk files, the default path is Path.GetTempPath()
    Timeout = 1000, // timeout (millisecond) per stream block reader, default values is 1000
    RequestConfiguration = // config and customize request headers
        Accept = "*/*",
        AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate,
        CookieContainer =  new CookieContainer(), // Add your cookies
        Headers = new WebHeaderCollection(), // Add your custom headers
        KeepAlive = false,
        ProtocolVersion = HttpVersion.Version11, // Default value is HTTP 1.1
        UseDefaultCredentials = false,
        UserAgent = $"DownloaderSample/{Assembly.GetExecutingAssembly().GetName().Version.ToString(3)}"

So, declare download service instance per download and pass your config:

var downloader = new DownloadService(downloadOpt);

Then handle download progress and completed events:

// Provide `FileName` and `TotalBytesToReceive` at the start of each downloads
downloader.DownloadStarted += OnDownloadStarted;    

// Provide any information about chunker downloads, like progress percentage per chunk, speed, total received bytes and received bytes array to live streaming.
downloader.ChunkDownloadProgressChanged += OnChunkDownloadProgressChanged;

// Provide any information about download progress, like progress percentage of sum of chunks, total speed, average speed, total received bytes and received bytes array to live streaming.
downloader.DownloadProgressChanged += OnDownloadProgressChanged;

// Download completed event that can include occurred errors or cancelled or download completed successfully.
downloader.DownloadFileCompleted += OnDownloadFileCompleted;    

Start the download asynchronously

string file = @"Your_Path\fileName.zip";
string url = @"https://file-examples.com/fileName.zip";
await downloader.DownloadFileTaskAsync(url, file);

Download into a folder without file name

DirectoryInfo path = new DirectoryInfo("Your_Path");
string url = @"https://file-examples.com/fileName.zip";
await downloader.DownloadFileTaskAsync(url, path); // download into "Your_Path\fileName.zip"

Download on MemoryStream

Stream destinationStream = await downloader.DownloadFileTaskAsync(url);

The ‍DownloadService class has a property called Package that stores each step of the download. To stopping or pause the download you must call the CancelAsync method, and if you want to continue again, you must call the same DownloadFileTaskAsync function with the Package parameter to resume your download! For example:

Keep Package file to resume from last download positions:

DownloadPackage pack = downloader.Package; 

Stop or Pause Download:


Resume Download:

await downloader.DownloadFileTaskAsync(pack); 

So that you can even save your large downloads with a very small amount in the Package and after restarting the program, restore it again and start continuing your download. In fact, the packages are your instant download snapshots. If your download config has OnTheFlyDownload, the downloaded bytes ​​will be stored in the package itself, but otherwise, only the downloaded file address will be included and you can resume it whenever you like. For more detail see StopResumeDownloadTest method

Note: for complete sample see Downloader.Sample project from this repository.

How to serialize and deserialize downloader package

Serialize and deserialize download packages to/from JSON text or Binary, after stopping download to keep download data and resuming that every time you want. You can serialize packages even using memory storage for caching download data which is used MemoryStream.

Serialize and Deserialize into Binary with BinaryFormatter

To serialize or deserialize the package into a binary file, just you need to a BinaryFormatter of IFormatter and then create a stream to write bytes on that:

DownloadPackage pack = downloader.Package; 
IFormatter formatter = new BinaryFormatter();
Stream serializedStream = new MemoryStream();

Serializing package:

formatter.Serialize(serializedStream, pack);

Deserializing into the new package:

var newPack = formatter.Deserialize(serializedStream) as DownloadPackage;

For more detail see PackageSerializationTest method

Serialize and Deserialize into JSON text with Newtonsoft.Json

Serializing the package to JSON is very simple like this:

var serializedJson = Newtonsoft.Json.JsonConvert.SerializeObject(pack);

But to deserializing the IStorage Storage property of chunks you need to declare a JsonConverter to override the Read method of JsonConverter. So you should add the below converter to your application:

public class StorageConverter : Newtonsoft.Json.JsonConverter<IStorage>
    public override void WriteJson(JsonWriter writer, IStorage value, JsonSerializer serializer)
        throw new NotImplementedException();

    public override IStorage ReadJson(JsonReader reader, Type objectType, IStorage existingValue, bool hasExistingValue, JsonSerializer serializer)
        if (reader.TokenType == JsonToken.Null)
            return null;

        var obj = JObject.Load(reader); // Throws an exception if the current token is not an object.
        if (obj.ContainsKey(nameof(FileStorage.FileName)))
            var filename = obj[nameof(FileStorage.FileName)]?.Value<string>();
            return new FileStorage(filename);

        if (obj.ContainsKey(nameof(MemoryStorage.Data)))
            var data = obj[nameof(MemoryStorage.Data)]?.Value<string>();
            return new MemoryStorage() { Data = data };

        return null;

Then you can deserialize your packages from JSON:

var settings = new Newtonsoft.Json.JsonSerializerSettings();
settings.Converters.Add(new StorageConverter());
var newPack = Newtonsoft.Json.JsonConvert.DeserializeObject<DownloadPackage>(serializedJson, settings);

For more detail see PackageSerializationTest method

Features at a glance

  • Download files async and non-blocking.
  • Cross-platform library to download any files with any size.
  • Get real-time progress info of each block.
  • Download file multipart as parallel.
  • Handle any client-side or server-side exception none-stopping the downloads.
  • Config your ChunkCount to define the parts count of the download file.
  • Download file multipart as in-memory or in-temp files cache mode.
  • Store download package object to resume the download when you want.
  • Get download speed or progress percentage in each progress event.
  • Get download progress events per chunk downloads.
  • Stop and Resume your downloads with package object.
  • Set a speed limit on downloads.
  • Live streaming support, suitable for playing music at the same time as downloading.
  • Download files without storing on disk and get a memory stream for each downloaded file.
  • Serialize and deserialize download packages to/from JSON text or Binary.


Welcome to contribute, feel free to change and open a PullRequest to develop branch.


You can use either the latest version of Visual Studio or Visual Studio Code and .NET CLI for Windows, Mac and Linux.

Note for Pull Requests (PRs): We accept pull request from the community. When doing it, please do it onto the develop branch which is the consolidated work-in-progress branch. Do not request it onto master branch.


FOSSA Status

*Note that all licence references and agreements mentioned in the Downloader README section above are relevant to that project's source code only.