asp.net MVC: How to redirect a non www to www and vice versa

I would like to redirect all www traffic to non-www traffic

I have copied this into my web.config

<system.webServer> / <rewrite> / <rules>

<rule name="Remove WWW prefix" >
<match url="(.*)" ignoreCase="true" />
<conditions>
<add input="{HTTP_HOST}" pattern="^www\.exam开发者_开发知识库ple\.com" />
</conditions>
<action type="Redirect" url="http://example.com/{R:1}"
    redirectType="Permanent" />
</rule>

per this post

How to redirect with "www" URL's to without "www" URL's or vice-versa?

but I got a 500 internal server error.

You might consider a different approach:

protected void Application_BeginRequest (object sender, EventArgs e)
{
   if (!Request.Url.Host.StartsWith ("www") && !Request.Url.IsLoopback)
   {
      UriBuilder builder = new UriBuilder (Request.Url);
      builder.Host = "www." + Request.Url.Host;
      Response.Redirect (builder.ToString (), true);
   }
}

This will however do a 302 redirect so a little tweak is recommended:

protected void Application_BeginRequest (object sender, EventArgs e)
{
   if (!Request.Url.Host.StartsWith ("www") && !Request.Url.IsLoopback)
   {
      UriBuilder builder = new UriBuilder (Request.Url);
      builder.Host = "www." + Request.Url.Host;
      Response.StatusCode = 301;
      Response.AddHeader ("Location", builder.ToString ());
      Response.End ();
   }
}

This one will return 301 Moved Permanently.

if you copied it directly then you have incorrect markup in your web.config

you need

<system.webServer>
    <rewrite>
      <rules>
        <rule name="Remove WWW prefix" >
        <match url="(.*)" ignoreCase="true" />
        <conditions>
        <add input="{HTTP_HOST}" pattern="^www\.example\.com" />
        </conditions>
        <action type="Redirect" url="http://example.com/{R:1}"
            redirectType="Permanent" />
        </rule>
      </rules>
    </rewrite>
<system.webServer>

The line that says

<system.webServer> / <rewrite> / <rules>

is stating that you need to put the config in that location within your web.Config. <system.webServer> is one of the configSections of your web.Config file.

Make sure you first have the URL Rewrite module installed for IIS7

The page above talks about redirecting HTTP to HTTPS, but the concept still applies for WWW to non WWW

Also, here is some detailed information on how it all comes together.

    **For a www to a non www Thanks @developerart**

protected void Application_BeginRequest(object sender, EventArgs e)
    {
        if (Request.Url.Host.StartsWith("www") && !Request.Url.IsLoopback)
        {
            UriBuilder builder = new UriBuilder(Request.Url);
            builder.Host = Request.Url.Host.Replace("www.","");
            Response.StatusCode = 301;
            Response.AddHeader("Location", builder.ToString());
            Response.End();
        }
    }

protected void Application_BeginRequest(object sender, EventArgs e)
{
    if (!this.Request.Url.Host.StartsWith("www") && !this.Request.Url.IsLoopback)
    {
        var url = new UriBuilder(this.Request.Url);
        url.Host = "www." + this.Request.Url.Host;
        this.Response.RedirectPermanent(url.ToString(), endResponse: true);
    }
}

You can use for https and www redirect. (You need to change "example")

<system.webServer>
  <!-- For force ssl and www -->
  <rewrite>
    <rules>
      <!-- For force ssl -->
      <rule name="http to https" stopProcessing="true">
        <match url="(.*)" />
        <conditions>
          <add input="{HTTPS}" pattern="^OFF$" />
        </conditions>
        <action type="Redirect" url="https://{HTTP_HOST}/{R:1}" redirectType="Permanent" />
      </rule>
      <!-- For force ssl -->
      <!-- For force www -->
      <rule name="redirect to www" stopProcessing="true">
        <match url="(.*)" />
        <conditions>
          <add input="{HTTP_HOST}"  pattern="^example\.com$" />
        </conditions>
        <action type="Redirect" url="https://www.{HTTP_HOST}/{R:0}" redirectType="Permanent" />
      </rule>
      <!-- For force www -->
    </rules>
  </rewrite>
  <!-- For force ssl and www -->
</system.webServer>

Building on user 151323' answer, here the complete answer for Azure users who also want to prevent users from accessing the site from a azurewebsites.net subdomain (this goes into your Global.asax inside the main class (MvcApplication for MVC users)):

    protected void Application_BeginRequest(object sender, EventArgs e)
    {
        if (Request.Url.Host.StartsWith("YourSite.azurewebsites") && !Request.Url.IsLoopback)
        {
            Response.StatusCode = 301;
            Response.AddHeader("Location", "www.example.com");
            Response.End();

            return;
        }

        if (!Request.Url.Host.StartsWith("www") && !Request.Url.IsLoopback)
        {
            UriBuilder builder = new UriBuilder(Request.Url);
            builder.Host = "www." + Request.Url.Host;
            Response.StatusCode = 301;
            Response.AddHeader("Location", builder.ToString());
            Response.End();
        }
    }

I know this thread is ancient and seems to be answered to death. But it may be useful to wrap everyone's global.asax suggestion with a check whether you are working locally or not. That way during development using IIS Express your site will not try and redirect to a 'www' sub-domain.

Something along the line of:

protected void Application_BeginRequest(
        object sender,
        EventArgs e)
    {
        if (!Request.IsLocal)
        {
            // Do your check for naked domain here and do permanent redirect
        }
    }

IIS can do it for you automatically:

Select site > URL rewrite > Add rule(s) > Canonical domain name

Choose primary domain and it is finished.

(If you do not have URL rewrite module installed, install it: https://www.iis.net/downloads/microsoft/url-rewrite)

You can achieve redirect non www to www at Server Level as well in IIS by writing the rule.

This rule will work but please note this rule will only work if you have installed URL Rewrite on your IIS Server. If URL Rewrite is not installed on your IIS Server then this rule will not work.

In order to install URL Rewrite on your server then go to this official website link and download the extension on your server and install it. After that restart the IIS Server and it will work.

URL Rewrite Extension Official Website Link: https://www.iis.net/downloads/microsoft/url-rewrite

<rewrite>
            <rules>
                <rule name="Redirect example.com to http://www.example.com HTTP" patternSyntax="ECMAScript" stopProcessing="true">
                    <match url=".*"></match>
                    <conditions>
                        <add input="{HTTP_HOST}" pattern="^example.com$"></add>
                        <add input="{HTTPS}" pattern="off"></add>
                    </conditions>
                    <action type="Redirect" url="http://www.example.com/{R:0}" redirectType="Permanent" appendQueryString="true"></action>
                </rule>
            </rules>
        </rewrite>