方法如下，引用自MSDN：
 
1.可执行文件：C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\aspnet_isapi.dll
  扩展名：.mspx
同时去掉确认文件存在前的勾
2.如果你的实际文件名是以.mspx结尾的，添加
<compilation>
         <buildProviders>
           <add extension=".mspx" type="System.Web.Compilation.PageBuildProvider"/>
         </buildProviders>
      </compilation>

<httpHandlers>
 <add verb="*" path="*.mspx" type="System.Web.UI.PageHandlerFactory"/>
</httpHandlers>
3. 如果你的实际文件名是以.aspx结尾的，在global.asax里（或者用urlrewrite）：
<%@ Application%>
<script language=C# runat="server">
  const string ASPX_EXT = ".aspx";
  const string MSPX_EXT = ".mspx";
  const string REWRITE_KEY = "Rewrite";
protected void Application_BeginRequest(Object sender, EventArgs E)
{
  string url = Context.Request.RawUrl.ToLower();
  if (url.IndexOf(MSPX_EXT) >0)
  {
Context.Items[REWRITE_KEY] = true;
url = url.Replace(MSPX_EXT,ASPX_EXT);
Context.RewritePath(url);
  }
}
protected void Application_PreRequestHandlerExecute(Object sender, EventArgs E)
{
if (Context.Items[REWRITE_KEY] != null)
Context.RewritePath(Context.Request.RawUrl);
}
</script>