An entry point cannot be marked with the 'async' modifier

Question

I copied below code from this link.But when I am compiling this code I am getting an entry point cannot be marked with the \'async\' modifier. How can I m

Answer 1

I'm using C# 8 and its working fine.

static async Task Main(string[] args)
{
   var response = await SomeAsyncFunc();
   Console.WriteLine("Async response", response);
}

OR without "await" keyword.

static void Main(string[] args)
{
   var response = SomeAsyncFunc().GetAwaiter().GetResult();
   Console.WriteLine("Async response", response);
}

Answer 2

Wrap your async code in MainAsync() - which is an async function
then call MainAsync().GetAwaiter().GetResult();

Answer 3

Starting from C# 7.1 there are 4 new signatures for Main method which allow to make it async(Source, Source 2, Source 3):

public static Task Main();
public static Task<int> Main();
public static Task Main(string[] args);
public static Task<int> Main(string[] args);

You can mark your Main method with async keyword and use await inside Main:

static async Task Main(string[] args)
{
    Task<string> getWebPageTask = GetWebPageAsync("http://msdn.microsoft.com");

    Debug.WriteLine("In startButton_Click before await");
    string webText = await getWebPageTask;
    Debug.WriteLine("Characters received: " + webText.Length.ToString()); 
}

C# 7.1 is available in Visual Studio 2017 15.3.

Answer 4

The error message is exactly right: the Main() method cannot be async, because when Main() returns, the application usually ends.

If you want to make a console application that uses async, a simple solution is to create an async version of Main() and synchronously Wait() on that from the real Main():

static void Main()
{
    MainAsync().Wait();
}

static async Task MainAsync()
{
    // your async code here
}

This is one of the rare cases where mixing await and Wait() is a good idea, you shouldn't usually do that.

Update: Async Main is supported in C# 7.1.

Answer 5

The difference between the code in the link's example and yours, is that you're trying to mark the Main() method with an async modifier - this is not allowed, and the error says that exactly - the Main() method is the "entry point" to the application (it's the method that is executed when your application starts), and it's not allowed to be async.