Using 'Async' in a Console Application in C#

Using 'async' in a console application in C#

In most project types, your async "up" and "down" will end at an async void event handler or returning a Task to your framework.

However, Console apps do not support this.

You can either just do a Wait on the returned task:

static void Main()
{
  MainAsync().Wait();
  // or, if you want to avoid exceptions being wrapped into AggregateException:
  //  MainAsync().GetAwaiter().GetResult();
}

static async Task MainAsync()
{
  ...
}

or you can use your own context like the one I wrote:

static void Main()
{
  AsyncContext.Run(() => MainAsync());
}

static async Task MainAsync()
{
  ...
}

More information for async Console apps is on my blog.

how to create async/await console app c# clock

By calling clock() from Main you are starting an asynchronous task without waiting for it to complete.

You can make clock() return a Task and use clock().Wait() block Main method until the task is completed (which will never be, because clock() contains an infinite loop and will never end).

Without Wait()ing for the task to complete, the Main will run to completion, causing the application to close.

using System;

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("Main 1");

        DoSomethingAsync().Wait();

        Console.WriteLine("Main 2");
    }

    public static async Task DoSomethingAsync()
    {
        Console.WriteLine("DoSomethingAsync 1");

        await Task.Delay(1000);

        Console.WriteLine("DoSomethingAsync 2");
    }
}

Output of the application:

Main 1
DoSomethingAsync 1
(delay of 1 second)
DoSomethingAsync 2
Main 2

Without Wait() it would have been:

Main 1
DoSomethingAsync 1
Main 2

or more likely it could have been:

Main 1
Main 2
DoSomethingAsync 1

C#: call async method inside Main of console application leads to compilation failure

Your Main method doesn't comply with one of the valid signatures listed here.

You probably want to use this:

public static async Task Main(string[] args)

A Task needs to be returned, so that the runtime knows when the method is complete; this couldn't be determined with void.

The compiler achieves this by generating a synthetic entry point:

private static void $GeneratedMain(string[] args) => 
    Main(args).GetAwaiter().GetResult();

async and await in console app

await Foo(); means that the rest of the method won't run until after the Task returned by Foo has completed. That's what it means to await something; the method won't continue until that Task has completed. As such, Console.WriteLine("----- Exit main"); won't run until after Foo has completed, which won't be until after it has already written out the time it took.

---

Related Topics