Async method with multiple tasks

Question

I'm trying to make my ASP.net Web API methods asynchronous. This method is in the Business Logic layer of my N-tier. I'm waiting for the result from my 1^st task and use it on the 2^nd task, but I think I'm doing it in a wrong way. Can you please give me advice or feedback regarding my code?

public async Task<DTOUser> CreateUser(DTORegister source)
{
    var result = new DTOUser();

    try
    {
        var user = new DTOUser()
        {
            Active = (int)defaultNumber.One,
            Deleted = (int)defaultNumber.Zero,
            DateCreated = DateTime.Now,
        };

        result = await Task.Run(() =>_RepositoryUser.Add<DTOUser, DTOUser>(user));

        //This part is where I dont feel confident
        var login = new DTOLogin()
        {
            Email = source.Email,
            Password = source.Password,
            OwnerID = result.UserID, //using the result of my 1st task here. 
            DateCreated = DateTime.Now

        };
        //use the login object to my 2nd task
        var task2 = await Task.Run(() =>_RepositoryLogIn.Add<DTOLogin, DTOLogin>(login));

        result.IsSuccessful = true;

    }
    catch (Exception ex)
    {
        result.ErrorMsg = "BL Error - " + ex.Message;
        result.IsSuccessful = false;
    }
    return result;
}

Both _RepositoryUser.Add and _RepositoryLogIn.Add are calling the same Generic Repository method from DAL:

public TOutPut Add<TOutPut, TInput>(TInput input)
        {
            var entityObj = MappingConfiguration.MapObjects<TInput, TType>(input); //Calling my automapper method to map my Entity object and DTO Object
            _entity.AddObject(this.GetEntitySetName(typeof(TType).Name), entityObj);
            _entity.SaveChanges();
            return MappingConfiguration.MapObjects<TType, TOutPut>(entityObj); 

        }

Answer 1

To me it seems like you are trying to make a async task for the sake of making it async to fit in with.

I'm trying to make my ASP.net Web API methods asynchronous

I don't see any reason for these pieces of code to be async. They aren't doing long running tasks and aren't even hitting the db (unless Add doesn't something we don't know about of course like saves as well which is a different point of review right there).

result = await Task.Run(() =>_RepositoryUser.Add<DTOUser, DTOUser>(user));

//use the login object to my 2nd task
var task2 = await Task.Run(() =>_RepositoryLogIn.Add<DTOLogin, DTOLogin>(login));

Once you have removed these, the method becomes a truly synchronous method. As it's a pretty trivial method anyway this shouldn't be a problem and making it async only confuses the issue for no benefit.

Answer 2

If that Add is calling the database, then async is warranted. However, I think you are overcomplicating it. With Async/Await, you need async/await through all the layers until you await a SaveChangesAsync or some bottom call.

Ultimately, when this async fires, it'll free up the thread for something else to do work. Also, if you are using a framework, you should do .ConfigureAwait(false) after all of your await calls or you could end up in deadlocks for users that force a sync call.

However, if you need the language/culture from the original thread later in the call, then you don't want to use ConfigureAwait(false), but you could always pull off the current values, run it, then update the thread values after the await call to fix that issue. Also, all the Async methods should have the word "Async" after them, except for the top level ones on the UI to make it clear.

This is how I'd lay it out:

public async Task<DTOUser> CreateUserAsync(DTORegister source)
{
    var result = new DTOUser();

    try
    {
        var user = new DTOUser()
        {
            Active = (int)defaultNumber.One,
            Deleted = (int)defaultNumber.Zero,
            DateCreated = DateTime.Now,
        };

        result = await _RepositoryUser.AddAsync<DTOUser, DTOUser>(user).ConfigureAwait(false);

        //This part is where I dont feel confident
        var login = new DTOLogin()
        {
            Email = source.Email,
            Password = source.Password,
            OwnerID = result.UserID, //using the result of my 1st task here. 
            DateCreated = DateTime.Now

        };

        await _RepositoryLogIn.AddAsync<DTOLogin, DTOLogin>(login).ConfigureAwait(false);

        result.IsSuccessful = true;

    }
    catch (Exception ex)
    {
        result.ErrorMsg = "BL Error - " + ex.Message;
        result.IsSuccessful = false;
    }
    return result;
}

_Repository.AddAsync, if using EF, would then await context.SaveChangesAsync().

If you wanted to go the extra mile, also have all methods take CancellationToken token = default(CancellationToken) as an optional parameter and pass that all the way down, too.