實體框架 - 「新的事物是不允許的，因爲有在會話中運行其他線程」

Question

我收到以下錯誤試圖保存在實體框架的變化 -

System.Data.SqlClient.SqlException：新事務不被允許，因爲會話中還有其他線程正在運行。

我見過各種各樣的回答這個問題，但我似乎無法得到其中的任何工作，基本上我保存在我的倉庫內交易的大量項目，我通過幾個項目具有循環刪除它們並編寫審計記錄。

我見過的所有其他答案（例如Mark Staffords Answer）都建議聲明一個顯式事務（我有）或者在完成循環後只調用保存更改（由於目前的審計方式，這不是一個選項 - 需要審計ID來編寫審計詳細記錄）。

每當「的SaveChanges」被稱爲刪除方法內部引發的錯誤，見下文 -

public virtual void Save(DoseReturn oldDoseReturn) 
{ 
    // Get the datetime when the save started 
    DateTime saveStartTime = DateTime.Now; 
    Dictionary<string, object> oldValues = new Dictionary<string, object>(); 
    Dictionary<string, object> newValues = new Dictionary<string, object>(); 

    // Get the object context and open a new transaction 
    ObjectContext objectContext = ((IObjectContextAdapter)context).ObjectContext; 
    objectContext.Connection.Open(); 
    DbTransaction transaction = objectContext.Connection.BeginTransaction(); 

    // Use the transaction for all updates 
    using (transaction) 
    { 
     if (oldDoseReturn != null) 
     { 
       IDoseReturnStatusRepository statusRepository = new DoseReturnStatusRepository(); 
       var list = statusRepository.AsQueryable().Where(x => x.DoseReturnID == oldDoseReturn.DoseReturnID); 

       foreach (var item in list) 
       { 
        statusRepository.Delete(item, objectRetrievedDateTime, objectContext, saveStartTime, out oldValues, out newValues); 
       } 

       context.SaveChanges(); 

       // Get the relevant repository 
       IDoseReturnsRepository repository = new DoseReturnsRepository(); 

       // audit and delete the object 
       repository.Delete(oldDoseReturn, objectRetrievedDateTime, objectContext, saveStartTime, out oldValues, out newValues); 

       context.SaveChanges(); 
     } 
    } 

    try 
    { 
     // Conduct a final save, then commit the transaction 
     context.SaveChanges(); 
     transaction.Commit(); 
    } 
    catch (Exception ex) 
    { 
     // An error has occurred, rollback the transaction and close the connection, then present the error 
     transaction.Rollback(); 
     objectContext.Connection.Close(); 
     throw ex; 
    } 
    // Close the connection 
    objectContext.Connection.Close(); 
} 

public virtual void Delete(T entity, DateTime? objectRetrievedDateTime, ObjectContext objectContext, DateTime saveStartTime, out Dictionary<string, object> oldValues, out Dictionary<string, object> newValues) 
    { 
     oldValues = new Dictionary<string, object>(); 
     newValues = new Dictionary<string, object>(); 

     if (entity == null) 
     { 
      throw new ArgumentException("Cannot update a null entity."); 
     } 

     string entityName = entity.GetType().Name; 

     if (!objectRetrievedDateTime.HasValue || !this.AuditsAfterRetieval(objectRetrievedDateTime, entityName, entity, saveStartTime)) 
     { 
      this.DeletedEntityAudit(entity, out oldValues, out newValues); 

      context.Entry(entity).State = System.Data.EntityState.Deleted; 
      this.context.Set<T>().Remove(entity); 
      this.Audit(entity, entityName, "Delete", oldValues, newValues, true); 
      this.context.SaveChanges(); 
     } 
     else 
     { 
      throw new Exception("Object cannot be saved as it has been amended in another thread"); 
     } 
    } 

Answer 1

這可能是因爲你試圖保存更改時列舉的結果。

嘗試改變這一行：

var list = statusRepository.AsQueryable() 
       .Where(x => x.DoseReturnID == oldDoseReturn.DoseReturnID); 

到：

var list = statusRepository.AsQueryable() 
       .Where(x => x.DoseReturnID == oldDoseReturn.DoseReturnID) 
       .ToList(); 

作爲一個側面說明調用.SaveChanges()一個循環中通常不是一個好主意，因爲它是在一般的昂貴的操作（會談到數據庫）。