字符串轉換爲在LINQ的GUID連接查詢：條件語句

我有LINQ查詢，如下字符串轉換爲在LINQ的GUID連接查詢：條件語句

using (RMPortalEntities _RMPortalEntities = new RMPortalEntities()) { 

       var _RSVP_ButtonLocations = _RMPortalEntities 
              .tbl_RSVP_ButtonLocation 
              .Join(_RMPortalEntities.tbl_RSVP_Setting, 
                  _RSVP_ButtonLocation => Guid.Parse(_RSVP_ButtonLocation.ID), 
                  _RSVP_Setting => _RSVP_Setting.RSVP_Button_Location_ID, 
                  (_RSVP_ButtonLocation, _RSVP_Setting) => new { _RSVP_ButtonLocation, _RSVP_Setting }) 
              .Join(_RMPortalEntities.tbl_Event, 
                  _RSVP_ButtonLocation_RSVP_Setting => _RSVP_ButtonLocation_RSVP_Setting._RSVP_Setting.EventID, 
                  _Event => _Event.ID, 
                  (_RSVP_ButtonLocation_RSVP_Setting, _Event) => new { _RSVP_ButtonLocation_RSVP_Setting, _Event }) 
              .Where(x => x._Event.Active == true 
                 && x._Event.ID == _EventID) 
              .Select(x => new 
              { 

               RSVP_ButtonLocations = x._RSVP_ButtonLocation_RSVP_Setting._RSVP_ButtonLocation.RSVP_ButtonLocation 

              }); 

       return _RSVP_ButtonLocations.FirstOrDefault().RSVP_ButtonLocations; 
      }

但問題是，LINQ查詢不允許我字符串轉換爲GUID值。任何人都可以給我建議嗎？

來源

2012-11-19 Frank Myat Thu

怎麼樣，而不是「Guid.Parse（_RSVP_ButtonLocation「新的GUID（_RSVP_ButtonLocation.ID）」。 ID）」？ – CjCoax

@CjCoax，我按照你的建議更新，我得到這個消息「System.NotSupportedException：LINQ to Entities只支持無參數的構造函數和初始值設定項。」「 –

@Frank，爲什麼用於連接的數據類型有所不同？也許最好是在兩個表中都有'Guid'？如果不是，可能你可以嘗試進行連接：將Guid轉換爲字符串，所以連接字符串值... – horgh

大廈CjCoax評論，你可以存儲GUID的一個實例，然後在後面的查詢中使用它：

using (RMPortalEntities _RMPortalEntities = new RMPortalEntities()) { 
      var GUID = new Guid(_RMPortalEntities.tbl_RSVP_ButtonLocation.ID); 
      var _RSVP_ButtonLocations = _RMPortalEntities 
             .tbl_RSVP_ButtonLocation 
             .Join(_RMPortalEntities.tbl_RSVP_Setting, 
                 _RSVP_ButtonLocation => GUID, 
                 _RSVP_Setting => _RSVP_Setting.RSVP_Button_Location_ID, 
                 (_RSVP_ButtonLocation, _RSVP_Setting) => new { _RSVP_ButtonLocation, _RSVP_Setting }) 
             .Join(_RMPortalEntities.tbl_Event, 
                 _RSVP_ButtonLocation_RSVP_Setting => _RSVP_ButtonLocation_RSVP_Setting._RSVP_Setting.EventID, 
                 _Event => _Event.ID, 
                 (_RSVP_ButtonLocation_RSVP_Setting, _Event) => new { _RSVP_ButtonLocation_RSVP_Setting, _Event }) 
             .Where(x => x._Event.Active == true 
                && x._Event.ID == _EventID) 
             .Select(x => new 
             { 

              RSVP_ButtonLocations = x._RSVP_ButtonLocation_RSVP_Setting._RSVP_ButtonLocation.RSVP_ButtonLocation 

             }); 

      return _RSVP_ButtonLocations.FirstOrDefault().RSVP_ButtonLocations; 
     }

來源

2012-11-19 04:05:45

'var GUID = new Guid（_RSVP_ButtonLocation.ID）;'因爲_RSVP_ButtonLocation聲明還沒有出現，所以我怎麼能使用這個語句？ –

如果我理解正確，編輯應該是你需要的 –

我感謝你的幫助@Sidharth Mudgal –

字符串轉換爲在LINQ的GUID連接查詢：條件語句

回答

相關問題