Asp.net 插入或更改查询字符串

  string InsertOrUpdateQueryStringItem(string key, string value)
         {
             if (Request.QueryString.HasKeys())
             {
                 if (!Array.Exists<string>(Request.QueryString.AllKeys, (qs) => { return qs.Equals(key); }))
                 {
                     return string.Format("{0}&{1}={2}", Request.RawUrl, key, value);
                 }
                 else
                 {
                     System.Text.StringBuilder pathBuilder = new System.Text.StringBuilder(Request.Path);
                     pathBuilder.Append("?");
                     string keyValue;
                     string keyCurrent;
                     int handedCount = ;

                     foreach (var k in Request.QueryString.AllKeys)
                     {

                         if (!k.Equals(key))
                         {
                             keyValue = Request.QueryString[k];
                             keyCurrent = k;
                         }
                         else
                         {
                             keyValue = value;
                             keyCurrent = key;
                         }

                         if (string.IsNullOrEmpty(keyValue))
                         {
                             continue;
                         }

                         if (handedCount++ != )
                         {
                             pathBuilder.AppendFormat("&{0}={1}", keyCurrent, keyValue);
                         }
                         else
                         {
                             pathBuilder.AppendFormat("{0}={1}", keyCurrent, keyValue);
                         }
                     }
                     return pathBuilder.ToString();
                 }
             }
             return string.Format("{0}?{1}={2}", Request.Path, key, value);
         }