When I initialise a portalSettings Object in my Web.API module using some portal ID, I get an object with a lot of sane properties, but the PortalAlias property is set to null.

DefaultPortalAlias = "dnndev.me"
PortalAlias = null
PortalAliasMappingMode = CanonicalUrl

This causes problems when the token [Portal:URL] is replaced, as this uses the PortalAlias.HTTPAlias property.
Is this a bug, should it be filled? (I would imagine that in a regular module the PortalAlias will be used to determine what the portalId is, just the other way around compared to a web service) Can I initialise the PortalAlias property with the DefaultPortalAlias property somehow? (or if this not the default alias of the specified portal, but the default for the host?)

 

I'm not sure what you're implying.

I've been able to 'fix' it by filling the PortalAliases property with the DefaultPortalAlias.

var portalSettings = new PortalSettings(portalId);
if (portalSettings.PortalAlias == null)
{
portalSettings.PortalAlias = new PortalAliasInfo();
portalSettings.PortalAlias.HTTPAlias = portalSettings.DefaultPortalAlias;
}
DotNetNuke.Services.Mail.Mail.SendMail(user, MessageType.UserRegistrationPublic, portalSettings);

Or make sure a default alias is selected for the portal. Which you can only set from an other portal (the problem was not that the portal had only one alias, the problem was that it was the current portal)