CSharpFunctionalExtensions.Errors

This library has the following errors classes

ErrorList

ErrorList To help return a collection of errors.

It can be used to combine multiple errors using the Combine method.

Example:

    var stringResultSuccess = Result.Success<string, ErrorList>("one");
    var emailResultFailure = EmailAddress.Create("Bad Email");
    var result = Result.Combine<ErrorList>(stringResultSuccess, emailResultFailure);

Common Error classes

The following error classes are available.

• Conflict
• NotFound
• Unauthorized
• Forbidden
• Unexpected
• Validation

Fluent Validation Extension

The following extension will convert Fluent Validation errors to ErrorList with Error.Validation errors.

public static Result<T, ErrorList> ToResult<T>(this FluentValidation.Results.ValidationResult validationResult, T value)
   

Example: Look at s_validator.Validate(user).ToResult(user); below.

public class User : Entity<Guid>
{
    public string FirstName { get; }
    public string LastName { get; }
    public string Email { get; }
    public string Password { get; }

    public static Result<User, ErrorList> Create(string firstName, string lastName, string email, string password)
    {
        var user = new User(firstName, lastName, email, password);
        return s_validator.Validate(user).ToResult(user);
    }


    private User(string firstName, string lastName, string email, string password)
    {
        FirstName = firstName;
        LastName = lastName;
        Email = email;
        Password = password;
    }

    static readonly InlineValidator<User> s_validator = new()
    {
        v => v.RuleFor(x => x.FirstName).NotEmpty(),
        v => v.RuleFor(x => x.LastName).NotEmpty(),
        v => v.RuleFor(x => x.Email).NotEmpty().EmailAddress(),
        v => v.RuleFor(x => x.Password).NotEmpty()
    };
}

CSharpFunctionalExtensions.Asp

ToActionResult extension method converts Result<T, Error> from CsharpFunctionalExtensions to Asp.Net Core ActionResult.

Run the sample program to try it out.

Example:

   public ActionResult<AuthenticationResult> Register(RegisterRequest request) =>
        Domain.User.Create(request.firstName, request.lastName, request.email, request.password)
             .Bind(user => Result.Success<AuthenticationResult, ErrorList>(new AuthenticationResult(user, "token")))
             .ToActionResult(this);

If a validation failure occurs, it will return a response like

HTTP/1.1 400 Bad Request
Connection: close
Content-Type: application/problem+json; charset=utf-8
Date: Mon, 14 Nov 2022 20:29:19 GMT
Server: Kestrel
Transfer-Encoding: chunked

{
  "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
  "title": "One or more validation errors occurred.",
  "status": 400,
  "traceId": "00-19b910c84bc8651a1c6d26e9ee640813-59f0f7943ce1d3ab-00",
  "errors": {
    "lastName": [
      "The lastName field is required."
    ],
    "firstName": [
      "The firstName field is required."
    ]
  }
}