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How to implement multi-tenancy with subdomains using Route Constraint in ASP.NET MVC




According to Wikipedia, The term "software multitenancy" refers to a software architecture in which a single instance of software runs on a server and serves multiple tenants. A tenant is a group of users who share a common access with specific privileges to the software instance. With a multitenant architecture, a software application is designed to provide every tenant a dedicated share of the instance - including its data, configuration, user management, tenant individual functionality and non-functional properties. Multitenancy contrasts with multi-instance architectures, where separate software instances operate on behalf of different tenants. By giving companies, access to a tenant through a subdomain of choice, will help to personalise the experience more and gives a sense of ownership to each tenant. This will go along way to bring consistency in there branding.

Implementing Route Constraint

You use route constraints to restrict the browser requests that match a particular route. To make this most easy, we shall be making our class to inherit the IRouteConstraint interface and this will help to route all specific tenant request. What then is an IRouteConstraint, according to msdn, IRouteConstraint Defines the contract that a class must implement in order to check whether a URL parameter value is valid for a constraint. The following implementation will get the tenant id and add it to route value dictionary.



public class RoutingConstraint : IRouteConstraint  
{
   public bool Match(HttpContextBase httpContext, Route route, string getParameter, RouteValueDictionary values, RouteDirection routeDirection)
   {
    var GetAddress = httpContext.Request.Headers["Host"].Split('.');
       if (GetAddress.Length < 2)
       {
           return false;
       }

       var tenant = GetAddress[0];
      
       if (!values.ContainsKey("tenant"))
       {
           values.Add("tenant", tenantId);
       }

       return true;
   }
}

Modify the Routes by adding the Route Constraints

routes.MapRoute(  
           name: "Default", url: "{controller}/{action}/{id}",
           defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional },
           constraints: new { TenantRouting = new RoutingConstraint() }
);

To get the tenant id from the controller that processes the request, simply add


public ActionResult Index()  
{
   var mytenant = this.RouteData.Values["tenant"]; // it will extract tenant data
   return View();
}



Summary

With the implementation, we can identify tenant specific data a user is trying to access.

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