Awaiting tasks from multiple objects

Question

I have an application that uses MEF to load plugins. All of these plugins conform to the following interface:

public interface IPlugin {
    Task Start();
}

All the methods are implemented as async: public async Task Start()

When the application is running I have an IEnumerable<IPlugin> property available with all the plugins. The question is basically how I can run all the Start() methods in parallel and wait until all methods are finished?

I know about Parallel.ForEach(plugins, plugin => plugin.Start()), but this is not awaitable and execution continues before all plugins are started.

The most promising solution seems to be Task.WhenAll(), but I don't know how to send in an unknown list of methods into this without adding some scaffolding (which seems like overhead).

How can I accomplish this?

Answer 1

And here's a one-liner:

await Task.WhenAll(plugins.Select(p => p.Start()));

The plugins will run asynchronously, but not in parallel. If you want for some reason to dispatch plugins to thread pool explicitly, you may add Task.Run with async lambda into Select.