C#•7mo ago

What should the service layer return back to a controller?

Confused about what the service layer should return to the controller, Dtos? Result object? Is this the correct approach?

public async Task<CreateUserResult> CreateUserAsync(string username, string email, string password)
{
    ...input validation

    username = username.ToLower();
    email = email.ToLower();

    if (_dbContext.Users.Any(x => x.Username.Equals(username)))
    {
        return; // Return a result object with a bool flag "IsDuplicateUsername"?
    }

    if (_dbContext.Users.Any(x => x.Email.Equals(email)))
    {
        return; // Return a result object with a bool flag "IsDuplicateEmail"?
    }

    var user = new User(username, email, password.ToHash());

    await _dbContext.Users.AddAsync(user);

    await _dbContext.SaveChangesAsync();
    
    // return result with everything false?
}

public async Task<CreateUserResult> CreateUserAsync(string username, string email, string password)
{
    ...input validation

    username = username.ToLower();
    email = email.ToLower();

    if (_dbContext.Users.Any(x => x.Username.Equals(username)))
    {
        return; // Return a result object with a bool flag "IsDuplicateUsername"?
    }

    if (_dbContext.Users.Any(x => x.Email.Equals(email)))
    {
        return; // Return a result object with a bool flag "IsDuplicateEmail"?
    }

    var user = new User(username, email, password.ToHash());

    await _dbContext.Users.AddAsync(user);

    await _dbContext.SaveChangesAsync();
    
    // return result with everything false?
}

17 Replies

Unknown User•7mo ago

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mg•7mo ago

It does

Unknown User•7mo ago

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mg•7mo ago

@ibby you could either return the created entity and rely on exceptions for error handling, or use a result monad like what OneOf provides Without knowing what your CreateUserResult is it's hard to say if it's right. I'm not sure what you mean by "return result with everything false" As @TeBeClone suggested, you should have username and email be unique on the database, and then you can just call SaveChangesAsync() inside a try/catch to do it all in one database round trip

mg•7mo ago

https://github.com/Giorgi/EntityFramework.Exceptions

GitHub

GitHub - Giorgi/EntityFramework.Exceptions: Handle database errors ...

Handle database errors easily when working with Entity Framework Core. Supports SQLServer, PostgreSQL, SQLite, Oracle and MySql. - Giorgi/EntityFramework.Exceptions

mg•7mo ago

And this will give you an exception that's specific to a unique constraint violation, rather than just a DbUpdateException

ibbyOP•7mo ago

This is what I was thinking at first with return a result. Everything false would mean success

public class CreateUserResult
{
    public bool IsUsernameTaken { get; set; } // will map to a BadRequest()
    public bool IsEmailAlreadyUsed { get; set; } // will map to a BadRequest()
    public bool IsError { get; set; } // will map to a StatusCode(500)
}

public class CreateUserResult
{
    public bool IsUsernameTaken { get; set; } // will map to a BadRequest()
    public bool IsEmailAlreadyUsed { get; set; } // will map to a BadRequest()
    public bool IsError { get; set; } // will map to a StatusCode(500)
}

I think I've seen something like this before, ill check it out. Thanks!

mg•7mo ago

I wouldn't do it that way. That requires you to have n different if statements to check each property in your controller

Unknown User•7mo ago

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mg•7mo ago

Whereas with OneOf you can have something like

return result.Match(user => user.MapToResponse(), conflict => conflict.MapToResponse(), error => error.MapToResponse())

return result.Match(user => user.MapToResponse(), conflict => conflict.MapToResponse(), error => error.MapToResponse())

where each different result type has its own mapping method to get mapped to a response And then you can reuse them in other requests too

Unknown User•7mo ago

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ibbyOP•7mo ago

this is the Result Pattern right?

Unknown User•7mo ago

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mg•7mo ago

Yeah that's what I meant, extension method

Unknown User•7mo ago

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mg•7mo ago

Or I mean it could be a member probably ¯\_(ツ)_/¯

Unknown User•7mo ago

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Gaming

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What should the service layer return back to a controller?