我应该如何处理服务层中的异常？

Question

I use DataAnnotations in my GUI layer to show error messages in forms, but I have some questions about how to handle exceptions from my service layer and what to show the user if they occur.

To communicate with my service layer I use a request and response class. For example:

public class RegisterUserRequest
{
    public string Username { get; set; }
    public string Password { get; set; }
    public string Email { get; set; }
}

Should I check for nulls in my request class inside the setter methods? Or should I do this in my service? I think it makes sense to do this on both the request and response setter methods and throw an ArgumentNullException if a parameter is null.

In my service class I throw an InvalidOperationException when for example the username or password is invalid. Is this the right exception to throw?

Another question I have is if I should catch all exceptions, and if so, what do I tell the user about the exception? If for example some property is null, it should throw an ArgumentNullException . But should I let the user know about this?

When an username is invalid I throw an InvalidOperationException . This one I do want to show to the user because it tells the user that it should use at least 3 characters or something.

I think I should use the error message from the InvalidOperationException to show to users and redirect to a standard error view when other exceptions occur like: "Oops, something went wrong".

Answer 1

我将再次使用DataAnnotations，因为如果没有人为用户名或密码输入错误的格式，则没人希望将其重定向到错误页面。

Answer 2

I think a more relevant exception to throw when the username or password is invalid is an ArgumentException. In the description of that exception type it specifically covers the case where an argument is invalid.

As for passing the exception to the user, you should try to inform the user of the error without exposing any of the inner workings of your service, so having a response message containing the error "Invalid username - must be at least 3 characters" will give them useful feedback.

For errors that you don't want to pass on in detail I would suggest logging an error message yourself and then passing the error ID to the user. eg "An unhandled error has occured. Please contact support, quoting error ID xxx". This should only be used as a last resort however - it is better to inform the user how to fix it but this would be a suitable way to catch all errors without passing too much information to the client.