最近一些使用URLRewriting的朋友们有时候会遇到asp.net Ajax和AJAX Control Toolkit控件不能正常工作的现象，对于没有相关经验的开发者来说相当棘手。本篇通过案例分析和相对的解决方案来讨论在使用ASP.NET AJAX 与 URLRewriting 时应当注意到的一些兼容性问题。
一般简单的URLRewriting应用都是对来自客户端对资源的Request进行路径重定向，比较典型的写法如同下列代码1 和代码2：
代码1：
// If the requested file exists if (File.Exists(Request.PhysicalPath)) { // Do nothing here, just serve the file } // If the file does not exist then else if (!File.Exists(Request.PhysicalPath)) { // Get the URL requested by the user string sRequestedURL = Request.Path.Replace(".aspx", "").Replace("/gratis24/",""); // You can retrieve the ID of the content from database that is // relevant to this requested URL (as per your business logic) string sId; sId = GetContentIDByPath(sRequestedURL); // The ShowContents.aspx page should show contents relevant to // the ID that is passed here string sTargetURL = "~/Kategori.aspx?category=" + sId; // Owing to RewritePath, the user will see requested URL in the // address bar // The second argument should be false, to keep your references // to images, CSS files Context.RewritePath(sTargetURL, false);
代码2：
//in global.asax void application_BeginRequest(object sender, EventArgs e) { System.Web.HttpContext httpContext = HttpContext.Current; String currentURL = httpContext.Request.Path.ToLower(); //Creates the physical path on the server string physicalPath = httpContext.Server.MapPath(currentURL.Substring(currentURL.LastIndexOf("/") + 1)); //checks to see if the file does not exsists. if (!System.IO.File.Exists(physicalPath) && !currentURL.EndsWith("webresource.axd")) { string reWritePage = "ViewPRofile.aspx"; httpContext.RewritePath(reWritePage); } }
然而，当我们使用上面的代码进行URLRewriting，并且在页面中使用ASP.NET AJAX 或 AJAX Control Toolkit的话，将会得到：'sys' is undefined 错误警告，而AJAX控件不能正常工作，totally not work.
很显然，'sys' is undefined 告诉我们 ASP.NET AJAX框架没有正常加载，根据分析可知，sys的定义是在脚本资源文件ScriptResource.axd中的，然而在上面的URLRewriting代码中，我们并没有对ScriptResource.axd进行特殊处理，导致该资源被重定向，没有正常加载。所以导致了ASP.NET AJAX不工作的问题。
知道了原因，我们就要修改URLRewriting的代码，为ScriptResource.axd增加一个例外：
代码1的解决方案：
在CheckPath时加入特例
private static void CheckPath(string path){ if (!string.Equals(path, VirtualPathUtility.ToAbsolute("~/ScriptResource.axd"), StringComparison.OrdinalIgnoreCase)) //it should be at the root. { Throw404(); }}
代码2的解决方案：
与1同理，在IO判断时加上特例，修改如下：
void Application_BeginRequest(object sender, EventArgs e) { System.Web.HttpContext httpContext = HttpContext.Current; String currentURL = httpContext.Request.Path.ToLower(); //Creates the physical path on the server string physicalPath = httpContext.Server.MapPath(currentURL.Substring(currentURL.LastIndexOf("/") + 1)); //checks to see if the file does not exsists. if (!System.IO.File.Exists(physicalPath) && !currentURL.EndsWith("webresource.axd") && !currentURL.EndsWith("ScriptResource.axd")) { string reWritePage = "ViewProfile.aspx"; httpContext.RewritePath(reWritePage); } }
至此，可解决该问题。
相关case：
http://forums.asp.net/t/1178119.aspx
http://forums.asp.net/p/1356089/2795441.aspx#2795441
Thanks.
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