大家应该知道，微软的URLRewrite能够对URL进行重写，但是也只能对域名之后的部分进行重写，而不能对域名进行重写，如：可将 http://http://www.abc.com//1234/  重写为 http://www.abc.com/show.aspx?id=1234  但不能将
http://1234.abc.com/  重写为  http://www.abc.com/show.aspx?id=1234。

要实现这个功能，前提条件就是  http://www.abc.com/ 是泛解析的，再就是要修改一下URLRewriter了。
总共要修改2个文件
1.BaseModuleRewriter.cs

protected virtual void BaseModuleRewriter_AuthorizeRequest(object sender, EventArgs e)
        {
            HttpApplication app = (HttpApplication) sender;
            Rewrite(app.Request.Path, app);
        }
改为

protected virtual void BaseModuleRewriter_AuthorizeRequest(object sender, EventArgs e)
        {
            HttpApplication app = (HttpApplication) sender;
            Rewrite(app.Request.Url.AbsoluteUri, app);
        }

就是将  app.Request.Path 替换成了  app.Request.Url.AbsoluteUri

2.ModuleRewriter.cs

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
                }
            }
改为

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 = "^" + 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
                }
            }
将

string lookFor = "^" + RewriterUtils.ResolveUrl(app.Context.Request.ApplicationPath, rules[i].LookFor) + "$";

改成了

string lookFor = "^" + rules[i].LookFor + "$";


完成这2处改动之后重新编译项目，将生成的dll复制到bin目录下。

再就是写web.config里的重写正则了

<RewriterRule>
            <LookFor>http://(\d+)\.abc\.com/</LookFor>
            <SendTo>/show.aspx?id=$1</SendTo>
        </RewriterRule>

好了大功告成，你在IE地址栏输入http://1234.abc.com/，就可以看到http://www.abc.com/show.aspx?id=1234

的结果了

若你在实际应用中碰到了问题，请查看文章 "修改UrlRewrite以对域名进行重写"需要注意的问题 ，希望能够帮助你！


附：

URLRewriter 的相关资料

http://www.microsoft.com/china/msdn/library/webservices/asp.net/URLRewriting.mspx