c# - Convert a method to use async

Question

I am converting a authentication process to support async and the VS 2015 IDE is warning me with the following message: The async method lacks 'await' operators and will run synchronously... etc...

Anyway, the code connects to a LDAP store and verifies a user's account and etc... I have tried various things with await, but I am just missing something here. I put the code back to what it was before.. I would appreciate any guidance in getting it to support async correctly...

Here is the code:

public async Task<User> GetAsyncADUser(PrincipalContextParameter param)
    {
        try
        {

            if (UseLDAPForIdentityServer3)
            {
                using (var pc = new PrincipalContext(ContextType.Domain, param.ADDomain, param.ADServerContainer, param.ADServerUser, param.ADServerUserPwd))
                {
                    UserPrincipal userPrincipal = UserPrincipal.FindByIdentity(pc, param.UserNameToValidate);
                    if (userPrincipal != null)
                    {
                        bool isvalid = pc.ValidateCredentials(userPrincipal.DistinguishedName, param.UserPasswordToValidate, ContextOptions.SimpleBind);

                        if (isvalid)
                        {
                            User user = new User { ad_guid = userPrincipal.Guid.ToString(), Username = param.UserNameToValidate, Password = param.UserPasswordToValidate };
                            return user;
                        }
                    }
                }
            }

        }
        catch (Exception ex)
        {
            throw;
        }

        return null;

    }

Answer 1

From MSDN:

The following characteristics summarize what makes an async method:

• The method signature includes an async modifier.

• The name of an async method, by convention, ends with an "Async" suffix. The return type is one of the following types:

  • Task<TResult> if your method has a return statement in which the operand has type TResult.
  • Task if your method has no return statement or has a return statement with no operand.
  • Void if you're writing an async event handler.

• The method usually includes at least one await expression, which marks a point where the method can't continue until the awaited asynchronous operation is complete. In the meantime, the method is suspended, and control returns to the method's caller. The next section of this topic illustrates what happens at the suspension point.

You can use return Task.Run(() => { /* your code here */ }) and return a Task<User>. Then you can call this method as :

User user = await GetAsyncADUser();

That way, you don't need to use the async keyword in the method GetAsyncADUser, but you need to mark the method that uses the above line of code with the async keyword.