In my previous post I have explained the importance of SEO and showed how to manipulate the meta tags and canonical URL from the code-behind files. Putting all that in place gets us only about half way there in terms of SEO, as we are still lacking one of the most important ingredients – URL rewrites.

Make no mistake – having a URL which is relevant to the content of the page and contains at least some of the keywords you target is a must if you want to achieve good search engine ranking. Even common sense dictates that it is better to send your visitors to http://yourshop.co.uk/products/great-product-everyone-wants-to-buy-as-it-has-a-nice-url.aspx than http://yourshop.co.uk/product.aspx?id=123…

There are multiple ways in which you can get URL rewrites working in your ASP.NET application. All of them are very well presented in Scott Guthrie’s blog post on the topic (http://weblogs.asp.net/scottgu/archive/2007/02/26/tip-trick-url-rewriting-with-asp-net.aspx).

The method that seemed to get the best compromise between flexibility and time needed for implementation is the one where you modify the global.asax file. I will briefly describe it below.

In the global.asax file (which you would need to add to your website, if it’s not already there) put the following code:

void Application_BeginRequest(object sender, EventArgs e)
    {
        try
        {
            string fullPath = Request.Url.ToString();

            //if the visitor requests a product page
            if (fullPath.Contains("/products/"))
            {
                using (MyDataContext db = new MyDataContext ())
                {
                    //split the url into segments
                    string[] segments = fullPath.Replace(".aspx", "").Split('/');
                    //the product alias is the last segment
                    string productAlias= segments[segments.Length - 2].ToLower();
                    //fetch a product with this alias
                    var products = db.Products.Where(p => p.Alias.ToLower() == productAlias);
                    if (products.Count() > 0)
                    {
                        var product= products.First();
                        //do the rewrite
                        Context.RewritePath("/product.aspx?id=" + product.ID.ToString());
                    }
                    else
                    {
                        //if no product was found redirect the visitor to the homepage
                        Response.Redirect("http://yourshop.co.uk");
                    }
                }
            }
        }
        catch(Exception){}
    }

The code above is quite basic, which should allow it to be easily edited/extended to fit your particular needs.

After you have the above code in place the rewrites should be working but you will probably hit a few problems. First of all, it is highly probable that your css won’t load and/or your links will be broken. The reason would be that you have put relative urls in your markup. You would need add a ‘/’ to the beginning of each url you are using to make sure it references the root of your website. For example, your css file path should be ‘/styles/style.css’ not ‘styles/style.css’.

Yet another problem you will hit sooner or later is the fact that the target url for your main <form> tag will not be rewritten. So every action performed by your visitors will send them to the ugly, not rewritten URLs, or even cause an error on your site. Fortunately, there is a quick and simple way to deal with this issue. You can modify the action attribute on your form control using a Form.browser file which you need place in the ‘App_Browsers’ folder in your website’s root. For more details on this please refer to the ScottGu’s blog post linked above.

After you have copied the Form.browser you need some code that will perform the actual logic of rewriting the action parameter. You will find both a CSharp and VisualBasic version of this code attached to this post. The vb version was provided by ScottGu in the aforementioned blog post, while the cs version was found on the dotnetguts blog. The file you need is called FormRewriter.cs (or FormRewriter.vb) and you need to place it in your ‘App_Code’ folder. Once you have those two files in place (Form.browser and the FormRewriter) everything should be back to normal and your form submissions should no longer cause any problems.