mvc-カスタムRoute

public class CustomerRoute : RouteBase
    {
　　　　　//       controller、action      ，  RouteData(    HttpHandler)，    HttpHandler    
        public override RouteData GetRouteData(System.Web.HttpContextBase httpContext)
        {
            var virtualPath = httpContext.Request.AppRelativeCurrentExecutionFilePath + httpContext.Request.PathInfo;//      

            virtualPath = virtualPath.Substring(2).Trim('/');//  URL  ～/ca-categoryname，     ca-categoryname

            if (!virtualPath.StartsWith("ca-"))//            URL，     null，        。
                return null;

            var categoryname = virtualPath.Split('-').Last();//  ca-        

            //              ，     
            var category = CategoryManager.AllCategories.Find(c => c.CategoeyName.Equals(categoryname, StringComparison.OrdinalIgnoreCase));

            if (category == null)//     null，          URL，  null，       
                return null;

            //             URL 
            var data = new RouteData(this, new MvcRouteHandler());//    RouteData，        
            data.Values.Add("controller", "CustomerRoute");
            data.Values.Add("action", "ShowCategory");
            data.Values.Add("id", category.CategoeyID);

            return data;//          CategoryController.ShowCategory(category.CategoeyID)  。    
        }

　　　　//  RouteValueDictionary   url
        public override VirtualPathData GetVirtualPath(RequestContext requestContext, RouteValueDictionary values)
        {
            //         CategoryController.Showcategory(string id),     null,     
            var categoryId = values["id"] as string;

            if (categoryId == null)//         id，          ，  null
                return null;

            //    CategoryController   ，          ，  null
            if (!values.ContainsKey("controller") || !values["controller"].ToString().Equals("CustomerRoute", StringComparison.OrdinalIgnoreCase))
                return null;
            //    CategoryController.Showcategory(string id)   ，          ，  null
            if (!values.ContainsKey("action") || !values["action"].ToString().Equals("showcategory", StringComparison.OrdinalIgnoreCase))
                return null;

            //  ，         CategoryController.Showcategory(string id)   ，     URL   
            var category = CategoryManager.AllCategories.Find(c => c.CategoeyID == categoryId);

            if (category == null)
                throw new ArgumentNullException("category");//         

            var path = "ca-" + category.CategoeyName.Trim();//  URL

            return new VirtualPathData(this, path.ToLowerInvariant());
        }
    }