Using the subdomain as a parameter

Question

I’ve got an ASP.net MVC (5.2) site that runs using several subdomains, where the name of the subdomain is the name of a client in my database. Basically what I want to do is use the subdomain as a variable within my action methods to allow me to get the correct data from my database.

I did something similar a few years back, but it’s messy and not intuitive, so was wondering if there’s a better way to do it than I was using before. Here’s what I did before:

protected override void OnActionExecuting(ActionExecutingContext filterContext) {
    Session["subdomain"] = GetSubDomain(Request.Url);
}

private static string GetSubDomain(Uri url) {
    string host = url.Host;
    if (host.Split('.').Length > 1) {
        int index = host.IndexOf(".");
        string subdomain = host.Substring(0, index);
        if (subdomain != "www") {
            return subdomain;
        }
    }
    return null;
}

Which basically assigned a key to the session variable if the subdomain was anything other than "www", but I’m really not happy with this way of doing it as it relies on me knowing that the session might contain this magic value!

Ideally I’d like to be able to create an attribute that I can decorate my classes/methods with that would extract the subdomain and then allow me to include a "subdomain" parameter in my action method that would contain the value extracted by the attribute. Is that even possible?

If that can’t be done, is there a better way of doing what I’m doing now without having to rely on the session?

Thanks,

Dylan

Answer 1

You could set the name in the Session on the Session_Start event in the global.asax, this means it would only happen one time and would persist for the duration of the users' session

public void Session_Start(object sender, EventArgs e)
{
    Session["subdomain"] = GetSubDomain(Request.Url);
}

Answer 2

Looks like there’s a good way of doing what I’m after at:

ASP.NET MVC Pass object from Custom Action Filter to Action

It essentially uses the route data to pass a custom parameter to the action, and can also pass objects other than simple strings etc.

On the plus side it avoids using the session and relying on magic values, but on the downside it means processing the URL for every request, which probably isn’t a good idea if a database is involved.

Answer 3

Your right this doesn't need to be stored in Session and IMHO shouldn't be, I would refactor this out into its own class and use HttpContext.Current.

public interface ISubDomainProvider
{
    string SubDomain { get; set; }
}


public class SubDomainProvider : ISubDomainProvider
{
    public SubDomainProvider()
    {
        string host = HttpContext.Current.Request.Url.Host; // not checked (off the top of my head
        if (host.Split('.').Length > 1) 
        {
            int index = host.IndexOf(".");
            string subdomain = host.Substring(0, index);
            if (subdomain != "www") 
            {
                SubDomain = subdomain;
            }
        }
    }

    public string SubDomain { get; set; }
}

You choose how to use it, if your using an IoC container it would just be a case of injecting this class into your controller via the constructor, I like this because it is easier to Mock and Unit Test. Of course you can still do this:

public class SomeController : Controller
{
    private readonly ISubDomainProvider _subDomainProvider;
    public SomeController()
    {
        _subDomainProvider = new SubDomainProvider();
    }
} 

You could even create you own abstract Controller Class:

public abstract class MyAbstractController : Controller
{
    public MyAbstractController()
    {
        SubDomain = new SubDomainProvider();
    }

    protected string SubDomain {get; set; }
}

public class SomeController : MyAbstractController
{
    public ActionResult SomeAction()
    {
        // access the subdomain by calling the base base.SubDomain 
    }
}