[Log]ASP.NET之HttpModule拦截404异常

Httpmodule代码：
public class Error404Module : IHttpModule
{
public void Init(HttpApplication context)
{
context.Error += new EventHandler(Context_Error);
}

protected void Context_Error(object sender, EventArgs e)
{
HttpContext ctx = HttpContext.Current;
HttpResponse response = ctx.Response;
HttpRequest request = ctx.Request;

Exception ex = ctx.Server.GetLastError();
HttpException hex = ex as HttpException;
if (hex != null && hex.GetHttpCode() == 404)
{
ctx.Server.ClearError();
string url = request.Url.AbsoluteUri.ToLower();
if (url.Contains(@"http://hj.woniu.com"))
{
url = url.Replace(@"http://hj.woniu.com", @"http://sg.hj.woniu.com");
}
response.Redirect(url, true);
}
}
public void Dispose()
{

}
}

Web.Config配置：
<httpModules>
<add name="Error404Module" type="ActHJ.ErrorModules.Error404Module"/>
</httpModules>

<system.web>
<compilation debug="false">
<assemblies>
<add assembly="System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
<add assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
<add assembly="System.Data.DataSetExtensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
<add assembly="System.Xml.Linq, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
</assemblies>
<buildProviders>
<add extension=".html" type="System.Web.Compilation.PageBuildProvider" />
<add extension=".htm" type="System.Web.Compilation.PageBuildProvider" />
</buildProviders>
</compilation>

<system.webServer>
<validation validateIntegratedModeConfiguration="false"/>
<modules>
<remove name="ScriptModule"/>
<add name="ScriptModule" preCondition="managedHandler" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
<add name="Error404Module" type="ActHJ.ErrorModules.Error404Module"/>
</modules>