上传文件太大（处理）

首先，在Global.asax.cs中实现Application_BeginRequest方法，实例HttpWorkerRequest wr = (HttpWorkerRequest)provider.GetService(typeof(HttpWorkerRequest))来获取web.config中的maxLength长度，同时开辟一个内存wr(大小为maxLength);然后用GetPreloadedEntityBody（）方法获取上传的文件的内容。对文件内容长度进行判断，如果文件大于2MB（request.ContentLength > 2097152），则用ReadEntityBody（）方法读取文件的n个字符，读入wr中，当读入的数据〉wr的大小时，Maximum request length exceeded异常触发。
于是在Global.asax.cs中实现Application_Error方法，判断如果获得的异常type为Maximum request length exceeded，则定位到错误页面(Error.asp)页面内容“上传的文件太大”。

 void Application_BeginRequest(object source, EventArgs e)
        {
              IServiceProvider provider = (IServiceProvider) HttpContext.Current;
              HttpWorkerRequest wr = (HttpWorkerRequest) provider.GetService(typeof(HttpWorkerRequest));
              byte[] bs = wr.GetPreloadedEntityBody();
             
              HttpRequest request = HttpContext.Current.Request;
              if (request.ContentLength > 2097152)
              {
                  if (!wr.IsEntireEntityBodyIsPreloaded())
                  {
                      int n = 65535;
                      byte[] bs2 = new byte[n];
                      while (wr.ReadEntityBody(bs2, n) > 0)
                      {
                      }

                  }
                  //Response.Redirect("~/About.aspx");
              }
        }

 

 void Application_Error(object sender, EventArgs e)
        {
            // Code that runs when an unhandled error occurs
            Exception exc = Server.GetLastError();
 
            // Handle HTTP errors
            if (exc.GetType() == typeof(HttpUnhandledException))
            {
                if (exc.InnerException.Message.Contains("Maximum request length exceeded."))
                    Response.Redirect("~/Error.aspx");

                //exc.InnerException.
            }
        }