Question

I’m looking at using ASP.NET for a new SaaS service, but for the love of me I can’t seem to figure out how to do account lookups based on subdomains like most SaaS applications (e.g. 37Signals) do.

For example, if I offer yourname.mysite.com, then how would I use ASP.NET (MVC specifically) to extract the subdomain so I can load the right template (displaying your company’s name and the like)? Can it be done with regular routing?

This seems to be a common thing in SaaS so there has to be an easy way to do it in ASP.NET; I know there are plugins that do it for other frameworks like Ruby on Rails.

Answer 1

This works for me:

    //--------------------------------------------------------------------------------------------------------------------------     public string GetSubDomain()     {         string SubDomain = '';          if (Request.Url.HostNameType == UriHostNameType.Dns)             SubDomain = Regex.Replace(Request.Url.Host, '((.*)(\\..*){2})|(.*)', '$2');         if (SubDomain.Length == 0)             SubDomain = 'www';         return SubDomain;     } 

I’m assuming that you would like to handle multiple accounts within the same web application rather than building separate sites using the tools in IIS. In our work, we started out creating a new web site for each subdomain but have found that this approach doesn’t scale well – especially when you release an update and then have to modify dozens of sites! Thus, I do recommend this approach rather than the server-oriented techniques suggested above based on several years worth of experience doing exactly what you propose.

The code above just makes sure that this is a fully formed URL (rather, say, than an IP address) and returns the subdomain. It has worked well for us in a fairly high-volume environment.