Keyvan Nayyeri wrote up an article (and HttpModule) on how he handles removing the www from the URI when people visit his site. I wrote something similar to this a while back for a site I develop. This particular company has about 10 domain names that all point to the companies main web site. Back in 2000, before I started working for the company, the search engines had indexed all of the domain names. While this may be good I have always been worried about duplicate content in Google's Index.

The code below is a toned down version of the HttpModule I use.

First, I have a config file that properly configures the module.

<forceDomain enabled="true" debug="false">
    <add value="localhost" />
    <add value="" />

The config file tells the module that the primary domain for the site is It then goes on to setup domain names that are not redirected. Naturally, we want localhost requests to not be redirected. For this example, is also used. (yes, I realize that isn't a domain it is a URI, but I am too lazy to go back and change things)

Now to the code of the HttpModule.

public class ForceDomain : System.Web.IHttpModule
        private ForceDomainConfiguration ForceDomainConfiguration;
        public void Init(HttpApplication app)
            app.BeginRequest += new EventHandler(this.OnBeginRequest);

        public void OnBeginRequest(Object source, EventArgs e)
            // grab the configuration
            ForceDomainConfiguration = ForceDomainConfiguration.GetConfig();

            // If disabled.. exit out.
            if (!ForceDomainConfiguration.ModuleEnabled)
            // get access to app and context
            HttpApplication app = (HttpApplication)source;
            HttpContext ctx = app.Context;

            // Get the PrimaryDomain the site operates with
            String DomainName = ForceDomainConfiguration.PrimaryDomain;
            if (String.IsNullOrEmpty(DomainName))
                throw new System.Exception("Primary Domain not set in config file. /Config/forceDomain/primaryDomain");

            DomainName = DomainName.ToLower();
            // If we are operating in the primary domain, then just get out of here.
            if (ctx.Request.Url.Host.ToLower() == DomainName)

            // loop through the ignoredDomains.

            // If we are supposed to ignore it, then break out
            foreach (String s in ForceDomainConfiguration.IgnoredDomains)
                if (ctx.Request.Url.Host.ToLower() == s.ToLower())

            // If we got this far, create the new URL and redirect
            StringBuilder sendTo = new StringBuilder();
            if (ctx.Request.IsSecureConnection)


            ctx.Response.Status = "301 Moved Permanently";
            ctx.Response.AddHeader("Location", sendTo.ToString());


        public void Dispose()

Like I said, the code above is a toned down version of the module I use. I also make reference to ForceDomainConfiguration.GetConfig() which is code that I haven't showed here. If anyone wants me to package this up just drop a comment and I will see what I can do.

[tags:ASP.NET, HttpModule]

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