UrlRewrite(URL重写）--ASP.NET中的实现

protected override void Rewrite(string requestedPath, System.Web.HttpApplication app)
        {
            // log information to the Trace object.
            app.Context.Trace.Write("ModuleRewriter", "Entering ModuleRewriter");

            // get the configuration rules
            RewriterRuleCollection rules = RewriterConfiguration.GetConfig().Rules;

            // iterate through each rule...
            for(int i = 0; i < rules.Count; i++)
            {
                // get the pattern to look for, and Resolve the Url (convert ~ into the appropriate directory)
                string lookFor = "^" + RewriterUtils.ResolveUrl(app.Context.Request.ApplicationPath, rules[i].LookFor) + "$";

                // Create a regex (note that IgnoreCase is set...)
                Regex re = new Regex(lookFor, RegexOptions.IgnoreCase);

                // See if a match is found
                if (re.IsMatch(requestedPath))
                {
                    // match found - do any replacement needed
                    string sendToUrl = RewriterUtils.ResolveUrl(app.Context.Request.ApplicationPath, re.Replace(requestedPath, rules[i].SendTo));

                    // log rewriting information to the Trace object
                    app.Context.Trace.Write("ModuleRewriter", "Rewriting URL to " + sendToUrl);

                    // Rewrite the URL
                    RewriterUtils.RewriteUrl(app.Context, sendToUrl);
                    break;        // exit the for loop
                }
            }

            // Log information to the Trace object
            app.Context.Trace.Write("ModuleRewriter", "Exiting ModuleRewriter");
        }

        public static RewriterConfiguration GetConfig()
        {
            if (HttpContext.Current.Cache["RewriterConfig"] == null)
                HttpContext.Current.Cache.Insert("RewriterConfig", ConfigurationManager.GetSection("RewriterConfig"));
            
            return (RewriterConfiguration) HttpContext.Current.Cache["RewriterConfig"];
        }


    /// <summary>
    /// Deserializes the markup in Web.config into an instance of the <see cref="RewriterConfiguration"/> class.
    /// </summary>
    public class RewriterConfigSerializerSectionHandler : IConfigurationSectionHandler 
    {
        /// <summary>
        /// Creates an instance of the <see cref="RewriterConfiguration"/> class. : IConfigurationSectionHandler 
        /// </summary>
        /// <remarks>Uses XML Serialization to deserialize the XML in the Web.config file into an
        /// <see cref="RewriterConfiguration"/> instance.</remarks>
        /// <returns>An instance of the <see cref="RewriterConfiguration"/> class.</returns>
        public object Create(object parent, object configContext, System.Xml.XmlNode section) 
        {
            // Create an instance of XmlSerializer based on the RewriterConfiguration type...
            XmlSerializer ser = new XmlSerializer(typeof(RewriterConfiguration));

            // Return the Deserialized object from the Web.config XML
            return ser.Deserialize(new XmlNodeReader(section));
        }

    }