当没有指定的案例可以处理时,在switch语句中抛出异常

Question

Let's say we have a function that changes a password for a user in a system in an MVC app.:

public JsonResult ChangePassword
    (string username, string currentPassword, string newPassword)
{
    switch (this.membershipService.ValidateLogin(username, currentPassword))
    {
        case UserValidationResult.BasUsername:
        case UserValidationResult.BadPassword:
            // abort: return JsonResult with localized error message        
            // for invalid username/pass combo.
        case UserValidationResult.TrialExpired
            // abort: return JsonResult with localized error message
            // that user cannot login because their trial period has expired
        case UserValidationResult.Success:
            break;
    }

    // NOW change password now that user is validated
}

membershipService.ValidateLogin() returns a UserValidationResult enum that is defined as:

enum UserValidationResult
{
    BadUsername,
    BadPassword,
    TrialExpired,
    Success
}

Being a defensive programmer, I would change the above ChangePassword() method to throw an exception if there's an unrecognized UserValidationResult value back from ValidateLogin():

public JsonResult ChangePassword
    (string username, string currentPassword, string newPassword)
{
    switch (this.membershipService.ValidateLogin(username, currentPassword))
    {
        case UserValidationResult.BasUsername:
        case UserValidationResult.BadPassword:
            // abort: return JsonResult with localized error message        
            // for invalid username/pass combo.
        case UserValidationResult.TrialExpired
            // abort: return JsonResult with localized error message
            // that user cannot login because their trial period has expired
        case UserValidationResult.Success:
            break;
        default:
            throw new NotImplementedException
                ("Unrecognized UserValidationResult value.");
            // or NotSupportedException()
            break;
    }

    // Change password now that user is validated
}

I always considered a pattern like the last snippet above a best practice. For example, what if one developer gets a requirement that now when users try to login, if for this-or-that business reason, they're suppose to contact the business first? So UserValidationResult's definition is updated to be:

enum UserValidationResult
{
    BadUsername,
    BadPassword,
    TrialExpired,
    ContactUs,
    Success
}

开发人员更改ValidateLogin()方法的主体以UserValidationResult.ContactUs在适用时返回新的枚举值(),但忘记更新ChangePassword().如果没有交换机中的例外,用户仍然可以在首次验证登录尝试时更改密码!

这只是我,还是这个default: throw new Exception()好主意？几年前我就看到了它,并且总是(在研究之后)认为这是一种最佳实践.

Answer 1

在这种情况下我总是抛出异常.考虑使用InvalidEnumArgumentException,在这种情况下提供更丰富的信息.