How to return errors from services?

Question

ASP.NET

Hello! Prompt, who as returns errors from Business layer? For example

public User Method(Guid id)
{
 if(id == Guid.Empty) throw new ArgumentException(" some message ");
 return findedUserById;
}

is it worth it to do so, is it worth using an exception, roughly speaking, to validate business rules? Who uses what methods, share

Answer 1

Another option is a special return class, a la ASP.NET MVC ActionResut.
Those. all methods return some Result class:

class Result<T> {
   public T Result {get; private set; }}
   public bool Success {get; private set; }}
   public IEnumerable<Exception> Errors { get ... }
   public string ErrorMessage {get ... } // этого можно и не делать

   private Result() {}
   public static Result<T> Success(T result) { return new Result() { Result = result, Success = true }; }
   public static Result<T> Fail(Exception ex) { return new Result() { Success = false, Errors = new List<Exception>() { ex }, ErrorMessage = ex.Message }; }
}

Answer 2

An exception is an exceptional situation that should not occur in normal operation. But if the absence of an object is possible, and this is a normal situation (non-exceptional), then this is not an exception, it is better to return null.
Example one - the method should return the current user. Of course, the current user must be, if it is not - this is an exception.
The second example is looking for a comment on a post. Nobody left a single comment, and if you search for the found comment user, then the user will not be found, but this is not an exception - it is normal to return null.
But it is possible that it is better to make the code so that the call to this method would not be called.

Answer 3

I create my own exception. If wcf is a service, then I create exceptions inherited from FaultException.