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Orleans is a framework that provides a straight-forward approach to building distributed high-scale computing applications, without the need to learn and apply complex concurrency or other scaling patterns.

It was created by Microsoft Research implementing the Virtual Actor Model and designed for use in the cloud.

Orleans has been used extensively running in Microsoft Azure by several Microsoft product groups, most notably by 343 Industries as a platform for all of Halo 4 and Halo 5 cloud services, as well as by a number of other projects and companies.


Installation is performed via NuGet. There are several packages, one for each different project type (interfaces, grains, silo, and client).

In the grain interfaces project:

PM> Install-Package Microsoft.Orleans.OrleansCodeGenerator.Build

In the grain implementations project:

PM> Install-Package Microsoft.Orleans.OrleansCodeGenerator.Build

In the server (silo) project:

PM> Install-Package Microsoft.Orleans.Server

In the client project:

PM> Install-Package Microsoft.Orleans.Client

Official Builds

The stable production-quality release is located here.

The latest clean development branch build from CI is located: here

Building From Source

Clone the sources from the GitHub repo

Run run the Build.cmd script to build the binaries locally, then reference the required NuGet packages from Binaries\NuGet.Packages\*.


Documentation is located here

Code Examples

Create an interface for your grain:

public interface IHello : Orleans.IGrainWithIntegerKey
  Task<string> SayHello(string greeting);

Provide an implementation of that interface:

public class HelloGrain : Orleans.Grain, IHello
  Task<string> SayHello(string greeting)
    return Task.FromResult($"You said: '{greeting}', I say: Hello!");

Call the grain from your Web service (or anywhere else):

// Get a reference to the IHello grain with id '0'.
var friend = GrainClient.GrainFactory.GetGrain<IHello>(0);

// Send a greeting to the grain and await the response.
Console.WriteLine(await friend.SayHello("Good morning, my friend!"));



This project is licensed under the MIT license.

Quick Links

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.