Error message "CS5001 Program does not contain a static 'Main' method suitable for an entry point"

Question

Unable to execute the following code error CS5001 Program does not contain a static 'Main' method suitable for an entry point

What does this error message mean?

class Program
{
    static async Task MainAsync(string[] args)
    {
        Account.accountTest accountTest = new Account.accountTest();

        bool result = await accountTest.CreateAccountAsync();
    }
}

Solution

It means that you don't have a suitable entry point for your application at the moment.

That code will nearly work with C# 7.1, but you do need to explicitly enable C# 7.1 in your project file:

<LangVersion>7.1</LangVersion>

or more generally:

<LangVersion>latest</LangVersion>

You also need to rename MainAsync to Main. So for example:

Program.cs:

using System.Threading.Tasks;

class Program
{
    static async Task Main(string[] args)
    {
        await Task.Delay(1000);
    }
}

ConsoleApp.csproj:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp2.0</TargetFramework>
    <LangVersion>7.1</LangVersion>
  </PropertyGroup>
</Project>

... builds and runs fine.

Comments

[Eldritch Conundrum]

I got the same error message because I had async void Main instead of async Task Main

[001]

added <langversion>latest</langversion> to myproject.csproj still getting the same error.

[Jon Skeet]

@001: See my edited answer - the LangVersion needs capital L and V, and you need to rename the method as well.

[Jon Skeet]

@Pascal: We need far more information than that to help you. Which exact version of the C# compiler (that's the important bit) are you using? What's the context?

[Pascal]

and that was the problem. After I found the Advanced button I saw its set to latest major version(default) which should mean 7.0. I set it directly to 7.2 c# compiler. Then it works :-)

[Steven Liekens]

What is the default LangVersion when left unspecified?

[Jon Skeet]

@StevenLiekens The latest major version - so 7.0 at the moment.

[Stuart]

This was it for me. Language versions can also be set in the Properties page > Build Tab > Advanced

[gaurav thakur]

@JonSkeet This works fine while building the code, but I get same error while trying to publish the app. Any workaround?

[Jon Skeet]

@gauravthakur: It's very hard to tell without any more information about what kind of project you're working with etc. I suggest you ask a new question with precise details.

[gaurav thakur]

Thanks @JonSkeet for your reply :). It was silly mistake on side. I had only change Language version for Debug build and Publish uses Release build.

[Wellspring]

I lost about 30 minutes before I realized that the release configuration needed the same tweak that got my Debug version compiling. :-)

[ccalboni]

For those still with errors with language set correctly: make sure your Main signature is correct, with Task as a return type instead of void. If, like me, you only add "async" keyword the signature is not valid.

[mokh223]

how about for aspnetcore console application project. there is no where to define the version.

[Jon Skeet]

@user2748728: I don't know exactly what you mean by "aspnetcore console application" but if you've got a project file, that's where you put the version. (And I haven't seen anything in .NET Core that doesn't have a project file.)

[Fandango68]

Cannot believe after all these years this is still the ONLY solution. And BTW, <LangVersion> is not even in VS2017 intellisense!

[Jon Skeet]

@Fandango68: With the latest versions of the .NET Core SDK (now that C# 8 has shipped) you don't need to specify the language version - at least not in VS2019.

[Brian Sweeney]

Oddly for me, choosing Latest Version did not work. I ended up setting it to the latest version by selecting it from the dropdown in the Advanced page. Makes no sense, but maybe worth a try if you're stuck.

[Jacob Robbins]

Changing Main's return type from void to Task is the piece I was missing.