LINQ Datacontext處理問題

我在下面的DAL方法中得到了Cannot access object: DataContext after it's been disposed。我認爲我可以打電話在那裏處理。 result是IEnumurable，我認爲這是導致這些問題的IQueryable。LINQ Datacontext處理問題

我在做什麼錯？如何SHOULD我正在處置我的DataContext。有沒有更好的回報，然後DataTable？這是一個桌面應用指向在SQL 2005

導致此錯誤

實施例方法 - >

public static DataTable GetEnrolledMembers(Guid workerID) 
    { 
     var DB = CmoDataContext.Create(); 

     var AllEnrollees = from enrollment in DB.tblCMOEnrollments 
          where enrollment.CMOSocialWorkerID == workerID || enrollment.CMONurseID == workerID 
          join supportWorker in DB.tblSupportWorkers on enrollment.EconomicSupportWorkerID 
           equals supportWorker.SupportWorkerID into workerGroup 
          from worker in workerGroup.DefaultIfEmpty() 
          select 
           new 
           { 
            enrollment.ClientID, 
            enrollment.CMONurseID, 
            enrollment.CMOSocialWorkerID, 
            enrollment.EnrollmentDate, 
            enrollment.DisenrollmentDate, 
            ESFirstName = worker.FirstName, 
            ESLastName = worker.LastName, 
            ESPhone = worker.Phone 
           }; 

     var result = from enrollee in AllEnrollees.AsEnumerable() 
        where (enrollee.DisenrollmentDate == null || enrollee.DisenrollmentDate > DateTime.Now) 
        //let memberName = BLLConnect.MemberName(enrollee.ClientID) 
        let lastName = BLLConnect.MemberLastName(enrollee.ClientID) 
        let firstName = BLLConnect.MemberFirstName(enrollee.ClientID) 
        orderby enrollee.DisenrollmentDate ascending, lastName ascending 
        select 
         new 
         { 
          enrollee.ClientID, 
          //MemberName = memberName, 
          LastName = lastName, 
          FirstName = firstName, 
          NurseName = BLLAspnetdb.NurseName(enrollee.CMONurseID), 
          SocialWorkerName = BLLAspnetdb.SocialWorkerName(enrollee.CMOSocialWorkerID), 
          enrollee.EnrollmentDate, 
          enrollee.DisenrollmentDate, 
          ESWorkerName = enrollee.ESFirstName + " " + enrollee.ESLastName, 
          enrollee.ESPhone 
         }; 
     DB.Dispose(); 

     return result.CopyLinqToDataTable(); 
    }

部分類哪裏創建在DataContext - >

partial class CmoDataContext 
{ 
    public static bool IsDisconnectedUser 
    { 
     get 
     { 
      return Settings.Default.IsDisconnectedUser; 
     } 
    } 

    public static CmoDataContext Create() 
    { 
     var cs = IsDisconnectedUser ? Settings.Default.CMOConnectionString : Settings.Default.Central_CMOConnectionString; 
     return  new CmoDataContext(cs); 
    }

來源

2010-04-14 Refracted Paladin

您在處理DataContext之後調用CopyLinqToDataTable。由於LINQ使用延遲執行，因此在處理DataContext後，它只在枚舉result時執行查詢。

您應該將您的DataContext置於包含return語句的using塊中。
這將在調用CopyLinqToDataTable後處理DataContext，避免出現問題。

例如：

using(var DB = CmoDataContext.Create()) { 
    //Execute queries 
    return result.CopyLinqToDataTable(); 
}

的using語句生成finally塊部署在DataContext在結束時using塊的。（即使有異常拋出）

來源

2010-04-14 18:01:54 SLaks

只要返回在'使用'我會沒事的？謝謝 – 2010-04-14 18:03:19

是的;你會沒事的。（除非你返回'IEnumerable'） – SLaks 2010-04-14 18:04:13

好吧，出於好奇，'IEnumerable'仍然會在這裏失敗？那麼你如何歸還？ – 2010-04-14 18:09:54

你應該使用類似的查詢ToList調用Dispose

來源

2010-04-14 18:02:19 Nagg

'List'可以綁定到'DataGrids'之類以及'DataTable'嗎？如果是的話，我會研究它。就我的返回類型而言，我正在尋找「具體」這個術語嗎？ – 2010-04-14 18:04:22

你就不能做到這一點，而不是之前？

... 
DataTable dt = result.CopyLinqToDataTable(); 
DB.Dispose(); 
return dt;

來源

2010-04-14 18:03:20

LINQ Datacontext處理問題

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