这几天接到一个用户需求，需要为一个在运行的基于Asp.Net Web Form的老系统增加审计日志。对于用户访问的界面上的每个按钮，都需要记录下来访问的用户名、时间、IP地址。我们不能修改这个系统，最后决定采用HttpHandler处理这个问题，示例代码如下：

using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace Plat.LogHandler
{
    public class Handler : IHttpHandlerFactory
    {
        public IHttpHandler GetHandler(HttpContext context, string requestType, string url, string pathTranslated)
        {
            PageHandlerFactory factory = (PageHandlerFactory)Activator.CreateInstance(typeof(PageHandlerFactory), true);
            try
            {
                IHttpHandler handler = factory.GetHandler(context, requestType, url, pathTranslated);
                if (handler is Page)
                {
                    Page page = handler as Page;

                    page.PreRenderComplete += new EventHandler(PreRenderComplete);
                    
                }
                

                return handler;
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }

        public void ReleaseHandler(IHttpHandler handler)
        {
            
        }

        private void PreRenderComplete(object sender,EventArgs e)
        {
            var page = sender as Page;
            if (page != null && page.IsPostBack)
            {
                var btn = getPostBackControlName(page);
                if (btn != null)
                {
                    WriteLog(page.Title, btn.Text , btn.ID);
                }
            }
        }

        private Button getPostBackControlName(Page page)
        {
            
                Control c = null;
                foreach (string ctl in page.Request.Form)
                {
                    
                        c = page.FindControl(ctl);
                    
                    if (c is System.Web.UI.WebControls.Button )
                    {
                        return c as Button;
                    }
                }
            return null;

        }

    }
}

还需要在Web.config中进行配置,在system.web中：

<httpHandlers>
      <add path="*.aspx" verb="*" type="Plat.LogHandler.Handler" />
</httpHandlers>

在system.webserver中

<handlers>
    <add path="*.aspx" verb="*" type="Plat.LogHandler.Handler" name="logHandler" />
</handlers>

采用这种方法，在没有修改原有系统代码的情况下，满足了用户的需求。