IIS7 URL Rewrite - Add “www” prefix

Question

How to force example.com to be redirected to www.example.com with URL rewriting in IIS7? What kind of rule should go into the web.config? Thanks.

Answer 1

This is Microsoft's sample for URL Rewrite Module 2.0 that redirects *.fabrikam.com to www.fabrikam.com

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <system.webServer>
        <rewrite>
            <rules>
                <rule name="Add www" patternSyntax="Wildcard" stopProcessing="true">
                    <match url="*" />
                    <conditions>
                        <add input="{HTTP_HOST}" pattern="www.fabrikam.com" negate="true" />
                    </conditions>
                    <action type="Redirect" url="http://www.fabrikam.com/{R:1}" />
                </rule>
            </rules>
        </rewrite>
    </system.webServer>
</configuration>

Answer 2

I'm not sure if this helps, but i opted to do this at the app level. Here's a quick action filter I wrote to do this.. Simply add the class somewhere in your project, and then you can add [RequiresWwww] to a single action or an entire controller.

public class RequiresWww : ActionFilterAttribute
    {
        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            HttpRequestBase req = filterContext.HttpContext.Request;
            HttpResponseBase res = filterContext.HttpContext.Response;

            //IsLocal and IsLoopback i'm not too sure on the differences here, but I have both to eliminate local dev conditions. 
            if (!req.IsLocal && !req.Url.Host.StartsWith("www") && !req.Url.IsLoopback)
            {
                var builder = new UriBuilder(req.Url)
                {
                    Host = "www." + req.Url.Host
                };

                res.Redirect(builder.Uri.ToString());

            }

            base.OnActionExecuting(filterContext);
        }
    }

Then

[RequiresWwww]
public ActionResult AGreatAction()
{
...
}

or

[RequiresWwww]
public class HomeController : BaseAppController 
{
..
..
}

Hope that helps someone. Cheers!

Answer 3

Not sure about the best possible way to do this, but I have a site with all old domains / subdomains running this web.config:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <system.webServer>
        <rewrite>
            <rules>
                <rule name="Transfer" stopProcessing="true">
                    <match url=".*" />
                    <action type="Redirect" url="http://www.targetsite.com/{R:0}" redirectType="Permanent" />
                </rule>
            </rules>
        </rewrite>
    </system.webServer>
</configuration>

Seems to get the job done.

Answer 4

To make it more generic you can use following URL Rewrite rule which working for any domain:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
    <rewrite>
        <rules>
              <rule name="Add WWW" stopProcessing="true">
              <match url="^(.*)$" />
              <conditions>
                 <add input="{HTTP_HOST}" pattern="^(?!www\.)(.*)$" />
              </conditions>
              <action type="Redirect" url="http://www.{C:0}{PATH_INFO}" redirectType="Permanent" />
           </rule>
        </rules>
    </rewrite>
</system.webServer>