最近在做项目遇到一个问题，在主页面点击某个按钮时打开一个页面，之前做法都是弹出一个页面，但是现在要求是打开一个tab页面而不是弹出方式打开，这个主页面会传querystring过去，根据T_equ参数去做判断要不要默认进去让页面处于新增状态；这个不难，关键问题是需求要求这个打开的tab页面当点刷新按钮时不做处于新增状态的处理，之前是根据Request.QueryString["T_equ"]来做判断的，只要有值就让页面处于新增状态，需求是：当刷新页面或者按f5键时不让页面处于新增状态。这样一来就难解决了。Request.QueryString是只读的不能删除。所以不能把这个给清空掉，后来又考虑到用session或者viewstate去做记录，以为是多个页面都是类似的功能，为了防止可能会定义重复的session或者viewstate所以这个方案也排除掉了。一下为两种解决方案：
一种是根据参数做重定向处理，重定项时把T_equ参数清空掉处理，另一种是主页面传过来菜单码和guid在弹出页面做记录，如果文件中存在这个菜单码和guid时就当做是刷新页面处理不让页面处于新增状态，如果没找到的话就让页面处于新增状态并向文件中写入记录mc和guid.
(1)第一种方案：
bool isKeyFound = false; // Vital to stop calling recursively
        string newQueryString = GetNewQueryString(Request.QueryString, "Refresh", out isKeyFound);
        if (isKeyFound && newQueryString.Length > 0)
        {
            Response.Redirect(Request.Path + "?" + newQueryString);
        }
public static string GetNewQueryString(System.Collections.Specialized.NameValueCollection queryString, string removeKey, out bool isKeyFound)
    {
        string returnVal = string.Empty;
        isKeyFound = false;
        //Build the new query string.
        for (int j = 0; j < queryString.Count; j++)
        {
            // Anything except the target key
             if (j!=3&&!queryString.GetKey(j).ToLower().Equals(removeKey.ToLower()))
             {
                returnVal += queryString.GetKey(j) + "=" + queryString.Get(j) + "&";
             }
            else
            {
                if (j != 3)
                {
                    isKeyFound = true;
                }
            }
        }
        //Remove the trailing '&'
        return returnVal.TrimEnd('&');
    }
(2)第二中方案：
 tequ = Request.QueryString["T_equ"] != null ? Request.QueryString["T_equ"].ToString() : string.Empty;
        mc = Request.QueryString["mc"] != null ? Request.QueryString["mc"].ToString() : string.Empty;
        guid = Request.QueryString["Guid"] != null ? Request.QueryString["Guid"].ToString() : string.Empty;
        bool isKeyFound = false;
        if (!String.IsNullOrEmpty(mc) && !String.IsNullOrEmpty(guid))
        {
            ReadFile(mc, guid,out isKeyFound);
            if (!String.IsNullOrEmpty(tequ) && !isKeyFound)
            {
                AddLoadExcuteScript("SetDefaultAddStatus();");
                WgSemUse.StrFunAfterClientInitSelect = "SetDefaultAddStatus";
                WriteFile(mc + "," +guid+",");
            }
        }
/// <summary>
    /// 根据mc和guid读取文件
    /// </summary>
    /// <param name="mc"></param>
    /// <param name="guid"></param>
    /// <param name="isKeyFound"></param>
    public void ReadFile(string mc, string guid, out bool isKeyFound)
    {
        string curr = HttpContext.Current.Request.PhysicalApplicationPath + "Document\\SemUseCertificateInfoUrl.txt";
        isKeyFound = false;
        if (File.Exists(curr))
        {
            FileStream fs = new FileStream(curr, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
            StreamReader tr = new StreamReader(curr, System.Text.Encoding.Default);
            tr.BaseStream.Seek(0, SeekOrigin.Begin);
            string strLine = tr.ReadToEnd().Trim();
            string[] temp = strLine.Split(',');
            if (temp.Length > 0)
            {
                for (int i = 0; i < temp.Length; i++)
                {
                    if (temp[i] == mc)
                    {
                        continue;
                    }
                    if (temp[i] == guid)
                    {
                        isKeyFound = true;
                        break;
                    }
                }
            }
            tr.Close();
            tr.Dispose();
        }
    }
    /// <summary>
    /// 写入文件
    /// </summary>
    /// <param name="data"></param>
    public void WriteFile(string data)
    {
        string curr = HttpContext.Current.Request.PhysicalApplicationPath + "Document\\SemUseCertificateInfoUrl.txt";
        bool isexist= File.Exists(curr);
        if (isexist)
        {
            //StreamWriter streamw = File.AppendText(@"" + HttpContext.Current.Request.PhysicalApplicationPath + "/SemUseCertificateInfoUrl.txt");
            StreamWriter streamw = File.AppendText(curr);
            streamw.WriteLine(data);
            streamw.Close();
            streamw.Dispose();
        }
        else
        {
            File.Create(curr).Close();
        }
    }