/// <summary>
/// 出错处理:写日志,导航到公共出错页面
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
protected void Application_Error(object sender, EventArgs e)
{
  if (Server.GetLastError() == null) return;
  Exception ex = Server.GetLastError().GetBaseException();
  string error = this.DealException(ex);
  DotNet.Common.Util.Logger.WriteFileLog(error, HttpContext.Current.Request.PhysicalApplicationPath + "LogFile");
  if (ex.InnerException != null)
  {
    error = this.DealException(ex);
    DotNet.Common.Util.Logger.WriteFileLog(error, HttpContext.Current.Request.PhysicalApplicationPath + "LogFile");
  }
  this.Server.ClearError();
  this.Response.Redirect("/Error.aspx");
}
/// <summary>
/// 处理异常，用来将主要异常信息写入文本日志
/// </summary>
/// <param name="ex"></param>
/// <returns></returns>
private string DealException(Exception ex)
{
  this.Application["StackTrace"] = ex.StackTrace;
  this.Application["MessageError"] = ex.Message;
  this.Application["SourceError"] = ex.Source;
  this.Application["TargetSite"] = ex.TargetSite.ToString();
  string error = string.Format("URl：{0}\n引发异常的方法：{1}\n错误信息：{2}\n错误堆栈：{3}\n",
    this.Request.RawUrl, ex.TargetSite, ex.Message, ex.StackTrace);
  return error;
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Text;
namespace DotNet.Common.WebForm
{
  using DotNet.Common.Util;
  /// <summary>
  /// 通用未捕获异常处理 
  /// </summary>
  public class AspNetUnhandledExceptionModule : IHttpModule
  {
    static object syncObj = new object();
    static bool isInit = false;
    public AspNetUnhandledExceptionModule()
    {
    }
    #region IHttpModule Methods
    public void Init(HttpApplication context)
    {
      lock (syncObj)
      {
        if (!isInit)
        {
          AppDomain.CurrentDomain.UnhandledException += new UnhandledExceptionEventHandler(OnUnhandledException);
          isInit = true;
        }
      }
    }
    public void Dispose()
    {
    }
    #endregion
    #region OnUnhandledException
    void OnUnhandledException(object o, UnhandledExceptionEventArgs e)
    {
      if (e.ExceptionObject == null) return;
      Exception ex = e.ExceptionObject as Exception;
      string error = string.Format("引发异常的方法：{0}\n错误信息：{1}\n错误堆栈：{2}\n",
              ex.TargetSite, ex.Message, ex.StackTrace);
      Logger.WriteFileLog(error, AppDomain.CurrentDomain.BaseDirectory + "LogFile");
    }
    #endregion
  }
}

<httpModules>
   <add name="AspNetUnhandledExceptionModule" type="DotNet.Common.WebForm.AspNetUnhandledExceptionModule, DotNet.Common.WebForm"></add>
</httpModules>

protected void Page_Load(object sender, EventArgs e)
{
  if (!IsPostBack)
  {
    System.Threading.ThreadPool.QueueUserWorkItem(new System.Threading.WaitCallback(Test), null);
  }
}
protected void Test(object state)
{
  int[] numArr = new int[100];
  numArr[100] = 100; //异常
}