What extra values does Stack Exchange OpenID support?

Question

I am trying to get the username / display name, but I have no idea what are the supported values. I got the email and realname, but I don't know what returns the username / display name.

Is there a documentation or something about this?

My current code:

public class StackExchangeOpenID : OpenIdClient
{
    public StackExchangeOpenID()
        : base("stackexchange", "https://openid.stackexchange.com")
    {

    }

    protected override Dictionary<string, string> GetExtraData(IAuthenticationResponse response)
    {
        FetchResponse fetchResponse = response.GetExtension<FetchResponse>();
        if (fetchResponse != null)
        {
            var extraData = new Dictionary<string, string>();
            extraData.Add("email", fetchResponse.GetAttributeValue(WellKnownAttributes.Contact.Email));
            extraData.Add("name", fetchResponse.GetAttributeValue(WellKnownAttributes.Name.FullName));

            // returned value: null
            //extraData.Add("username", fetchResponse.GetAttributeValue(WellKnownAttributes.Name.Alias));

            return extraData;
        }

        return null;
    }
    protected override void OnBeforeSendingAuthenticationRequest(IAuthenticationRequest request)
    {
        var fetchRequest = new FetchRequest();
        fetchRequest.Attributes.AddRequired(WellKnownAttributes.Contact.Email);
        fetchRequest.Attributes.AddRequired(WellKnownAttributes.Name.FullName);

        // returned value: null
        //fetchRequest.Attributes.AddRequired(WellKnownAttributes.Name.Alias);

        request.AddExtension(fetchRequest);
    }
}

Answer 1

What's your arrow is pointing to their isn't a display name (StackID has no notion of display names, your login is your email address) but an optional "Vanity Id".

For example:

Gives me the vanity OpenID of https://openid.stackexchange.com/kevin.montrose . This is just an easier to remember alias for relying parties that require manual entry of OpenID urls.

Email and Real Name/Full Name are the only attributes StackID supports querying for, and will return both via either SREG or AX extensions (as seen in the code).