WCF WebApi, what is the correct way to handle IsThisTaken query?

Question

I am in the process of writing a WCF webapi application and have a need to check whether an email address is taken or not. This needs to be a query the client-side code can do before attempting a PUT.

So, what I'm trying to do is use HEAD in conjunction with HTTP status codes. I am a little unsure how to go about doing that as it's a simple yes/no response which is required. So, I've used HttpResponseExceptions to return the relevant status code.

    [WebInvoke(Method = "HEAD", UriTemplate = "{email}")]
    [RequireAuthorisation]
    public void IsEmailAddressTaken(string email)
    {
        if (!Regex.IsMatch(email, Regexes.EmailPattern))
        {
            throw new RestValidationFailureException("email", "invalid email address");
        }

        if (_repository.IsEmailAddressTaken(email))
        {
            throw new HttpResponseException(HttpStatusCode.OK);
        }

        throw new HttpResponseException(HttpStatusCode.NoContent);
    }

This just doesn't "smell" right to me.

am I going about doing this kind of yes/no operation the right way?

Alexander Zeitler · Answer 1 · 2012-01-17T21:59:16.547

2

I think it would be ok to just return OK for "exists" and 404 for "does not exist"

edited Jan 17 '12 at 21:59

answered Jan 17 '12 at 21:45

Alexander Zeitler

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The reason I wanted a "pre check" is so that the user can immediately see that the email is already taken without having to fill in the rest of the information on a registration page. So, we can go straight to the "reset password" page instead. I know I get annoyed when I go enter all my information only to be told "this email address has already been used". At which point I remember I already have an account! – Antony Scott Jan 17 '12 at 21:51

score 2 · Accepted Answer · edited Jan 18 '12 at 12:11

2

My suggestion is to return a HttpResponseMessage instead of throwing exceptions. Is your RestValidationFailureException being handled anywhere? If not, it will result in a 500 status code, which does not seem adequate.

edited Jan 18 '12 at 12:11

Antony Scott

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answered Jan 18 '12 at 11:26

Pedro Felix

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thanks. I'd just got there myself :) I think I was probably adding my solution to my question as your were typing this answer. – Antony Scott Jan 18 '12 at 12:12

WCF WebApi, what is the correct way to handle IsThisTaken query?

2 Answers2