Creating own Task returning methods in ASP.NET Core Web API

Question

I'm creating a simple authentication handler to be used with an ASP.NET Core Web API using the instructions of an article. The following code is a part of this work.

public class CustomAuthenticationHandler : AuthenticationHandler<BasicAuthenticationOptions>
{
    //Constructors and fields

    protected override async Task<AuthenticateResult> HandleAuthenticateAsync()
    {
        //Validation of bearer token 
        //No awaitable method calls
    }
}

Although this HandleAuthenticateAsync() method is marked as async, it doesn't actually await anything inside the method body at all. So, my questions are,

Do I really need to use a method decorated with async for this? Would it affect the application if I omitted the async keyword?
Can I rearrange this method which returns a Task<AuthenticateResult> in the following way without violating the best practices described in docs.

protected override Task<AuthenticateResult> HandleAuthenticateAsync()
    {
        return new Task<AuthenticateResult>(() =>
        {
            //Token validation
        });
    }

Stephen Cleary · Accepted Answer · 2022-12-21 13:43:20Z

2

Do I really need to use a method decorated with async for this? Would it affect the application if I omitted the async keyword?

I recommend that you do keep the async keyword, and use a # to silence the compiler warning. With task-returning methods, any exceptions should be caught and placed on the returned task, and async will do that for you so you don't have to write that code yourself.

Can I rearrange this method which returns a Task in the following way

No. You should never use the Task constructor.

If you don't want to use async, then return results using Task.FromResult and return exceptions using Task.FromException.

answered Dec 21, 2022 at 13:43

Stephen Cleary

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Comments

NazaRN · Accepted Answer · 2022-12-21 13:19:11Z

0

You don't need to decorate that method with async at all. Only if you will have something to be awaited there.

Your second point - you can totally do that but it hinders readability.

You can just follow the tutorials, which say the following: If something is wrong and Authentication cannot be done, return the following:

return Task.FromResult(AuthenticateResult.Fail("Cannot Auth"));

If everything is good, just return

return Task.FromResult(AuthenticateResult.Success(ticket));

The ticket being the AuthenticationTicket for the principal authenticating.

More info here: Authentication scheme in ASP.NET Core

answered Dec 21, 2022 at 13:19

NazaRN

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