using System;
using System.Collections.Generic;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.SessionState;
using System.Configuration;
namespace MyHttp
{
  public class UrlReWrite : IHttpModule
  {
    /// <summary>
    /// 单个IP最大连接限制数量
    /// </summary>
    private int rowCount = Convert.ToInt32(ConfigurationSettings.AppSettings["HttpRowCount"]);
    /// <summary>
    /// 指定区域时间范围 单位分
    /// </summary>
    private int httpTime = Convert.ToInt32(ConfigurationSettings.AppSettings["HttpTime"]);
    public void Init(HttpApplication application)
    {
      application.BeginRequest += (new
         EventHandler(this.Application_BeginRequest));
      application.EndRequest += (new
         EventHandler(this.Application_EndRequest));
    }
    private void Application_BeginRequest(Object source, EventArgs e)
    {
      HttpApplication Application = (HttpApplication)source;
      HttpContext ctx = Application.Context;
      //IP地址
      string isIp = ctx.Request.UserHostAddress;
      if (ctx.Application["time"] == null)
      {
        ctx.Application["time"] = DateTime.Now;
      }
      else
      {
        DateTime isTime = (DateTime)ctx.Application["time"];
        int timeTract = Convert.ToInt32(DateTime.Now.Subtract(isTime).Minutes.ToString());
        if (timeTract > (httpTime - 1))
        {
          ctx.Application["time"] = null;
          ctx.Application["myip"] = null;
        }
      }
      if (ctx.Application["myip"] != null && ctx.Application["myip"] is CartIp)
      {
        CartIp cartIp = (CartIp)ctx.Application["myip"];
        cartIp.Insert(isIp);
        ctx.Application["myip"] = cartIp;
        if (cartIp.GetCount(isIp) > rowCount)
        {
          ctx.Response.Clear();
          ctx.Response.Close();
        }
      }
      else
      {
        CartIp cartIp = new CartIp();
        cartIp.Insert(isIp);
        HttpContext.Current.Application["myip"] = cartIp;
      }
    }
    private void Application_EndRequest(Object source, EventArgs e)
    {
    }
    public void Dispose()
    {
    }
  }
}

using System;
using System.Collections.Generic;
using System.Text;
namespace MyHttp
{
  [Serializable]
  public class ListIp
  {
    private string ip;
    private int count;
    /// <summary>
    /// IP地址
    /// </summary>
    public string IP
    {
      get { return ip; }
      set { ip = value; }
    }
    /// <summary>
    /// 累加数量
    /// </summary>
    public int Count
    {
      get { return count; }
      set { count = value; }
    }
  }
  [Serializable]
  public class CartIp
  {
    public CartIp()
    {
      if (_listIp == null)
      {
        _listIp = new List<ListIp>();
      }
    }
    private List<ListIp> _listIp;
    public List<ListIp> _ListIp
    {
      get { return _listIp; }
      set { _listIp = value; }
    }
    /// <summary>
    /// 添加IP
    /// </summary>
    public void Insert(string ip)
    {
      int indexof = ItemLastInfo(ip);
      if (indexof == -1)
      {
        //不存在
        ListIp item = new ListIp();
        item.IP = ip;
        _listIp.Add(item);
      }
      else
      {
        _listIp[indexof].Count += 1;
      }
    }
    //判断IP是否存在
    public int ItemLastInfo(string ip)
    {
      int index = 0;
      foreach (ListIp item in _ListIp)
      {
        if (item.IP == ip)
        {
          return index;//存在
        }
        index += 1;
      }
      return -1;//不存在
    }
    /// <summary>
    /// 获得IP的数量
    /// </summary>
    /// <param name="ip"></param>
    /// <returns></returns>
    public int GetCount(string ip)
    {
      foreach (ListIp item in _ListIp)
      {
        if (item.IP == ip)
        {
          return item.Count;//存在
        }
      }
      return -1;//不存在
    }
  }
}

<appSettings>
<add key="HttpRowCount" value="100"/>
<add key="HttpTime" value="10"/>
</appSettings>
<system.web>
  <httpModules>
  <add name="UrlReWrite" type="MyHttp.UrlReWrite"/>
 </httpModules>
</system.web>