create filter to ensure lowercase urls - asp.net-mvc-4

Question

I have the following code in the global.asax of my mvc web application:
/// <summary>
/// Handles the BeginRequest event of the Application control.
/// </summary>
/// <param name="sender">The source of the event.</param>
/// <param name="e">The <see cref="EventArgs" /> instance containing the event data.</param>
protected void Application_BeginRequest(object sender, EventArgs e)
{
// ensure that all url's are of the lowercase nature for seo
string url = Request.Url.ToString();
if (Request.HttpMethod == "GET" && Regex.Match(url, "[A-Z]").Success)
{
Response.RedirectPermanent(url.ToLower(CultureInfo.CurrentCulture), true);
}
}
What this achieves is to ensure all url's accessing the site are in lower case. I would like to follow the MVC pattern and move this to a filter that can applied globally to all filters.
Is this the correct approach? And how would I create a filter for the above code?

Answer 1

My opinion - a filter is too late to handle a global url rewrite. But to answer your question as to how, create an action filter:
public class LowerCaseFilterAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
// ensure that all url's are of the lowercase nature for seo
var request = filterContext.HttpContext.Request;
var url = request.Url.ToString();
if (request.HttpMethod == "GET" && Regex.Match(url, "[A-Z]").Success)
{
filterContext.Result = new RedirectResult(url.ToLower(CultureInfo.CurrentCulture), true);
}
}
}
and in FilterConfig.cs, register your global filter:
public class FilterConfig
{
public static void RegisterGlobalFilters(GlobalFilterCollection filters)
{
filters.Add(new HandleErrorAttribute());
filters.Add(new LowerCaseFilterAttribute());
}
}
HOWEVER, I would recommend pushing this task out to IIS and using a rewrite rule. Make sure the URL Rewrite Module is added to IIS and then add the following rewrite rule in your web.config:
<!-- http://ruslany.net/2009/04/10-url-rewriting-tips-and-tricks/ -->
<rule name="Convert to lower case" stopProcessing="true">
<match url=".*[A-Z].*" ignoreCase="false" />
<conditions>
<add input="{REQUEST_METHOD}" matchType="Pattern" pattern="GET" ignoreCase="false" />
</conditions>
<action type="Redirect" url="{ToLower:{R:0}}" redirectType="Permanent" />
</rule>