Are async console applications supported in .NET Core?
Solution 1:
Yes, the async Main
functions are supported since .NET Core 2.0
.
dotnet --info
.NET Command Line Tools (2.0.0)
Product Information:
Version: 2.0.0
Commit SHA-1 hash: cdcd1928c9
Runtime Environment:
OS Name: ubuntu
OS Version: 16.04
OS Platform: Linux
RID: ubuntu.16.04-x64
Base Path: /usr/share/dotnet/sdk/2.0.0/
Microsoft .NET Core Shared Framework Host
Version : 2.0.0
Build : e8b8861ac7faf042c87a5c2f9f2d04c98b69f28d
The support for the async Main
functions is introduced in C# version 7.1. However, this functionality is not available out of the box. To make use of this feature you need explicitly specify the C# version 7.1 in your .csproj
file, either by including
<LangVersion>latest</LangVersion>
or by
<LangVersion>7.1</LangVersion>
For example for the ASP.NET core 2.0 project:
<Project Sdk="Microsoft.NET.Sdk.Web">
<PropertyGroup>
<TargetFramework>netcoreapp2.0</TargetFramework>
<LangVersion>latest</LangVersion>
</PropertyGroup>
<ItemGroup>
<PackageReference Include="Microsoft.AspNetCore.All" Version="2.0.0" />
</ItemGroup>
<ItemGroup>
<DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="2.0.0" />
<DotNetCliToolReference Include="Microsoft.EntityFrameworkCore.Tools.DotNet" Version="2.0.0" />
<DotNetCliToolReference Include="Microsoft.DotNet.Watcher.Tools" Version="2.0.0" />
</ItemGroup>
</Project>
where the Main function can be rewritten as following:
using System.Threading.Tasks;
...
public static async Task Main(string[] args)
{
await BuildWebHost(args).RunAsync();
}
...
References:
- C# 7 Series, Part 2: Async Main
- Champion "Async Main" (C# 7.1)
Solution 2:
Update: Async main is supported natively by C# 7.1! See Evgeny's answer above.
I'll keep the below workaround for posterity, but it is no longer needed. async main
is way simpler, use that if you can!
This is my preferred workaround in C# less than 7.1:
using System;
using System.Threading.Tasks;
namespace ConsoleApplication
{
public class Program
{
public static void Main(string[] args)
{
MainAsync(args).GetAwaiter().GetResult();
Console.ReadKey();
}
public static async Task MainAsync(string[] args)
{
await Task.Delay(1000);
Console.WriteLine("Hello World!");
}
}
}
GetAwaiter().GetResult()
is the same as .Wait
(blocking synchronously), but is preferred because it unwraps exceptions.