实体框架异常: SqlConnection不支持并行事务

Question

我们有一个处理XML文件的应用程序。应用程序使用EF 6将数据保存到DB。应用程序使用ThreadPool.QueueUserWorkItem方法处理并发线程中的文件。申请期为1，5年，效果良好。现在我们开始获得EF异常，如下所示：

大多数情况下，没有这样的错误，但它是一天几次。我们成功地找出了导致EF产生此错误的原因或条件。

有什么建议吗？

 An error occurred while starting a transaction on the provider connection. See the inner exception for details.
   at System.Data.Entity.Core.EntityClient.EntityConnection.BeginDbTransaction(IsolationLevel isolationLevel)
   at System.Data.Entity.Core.EntityClient.EntityConnection.BeginTransaction()
   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)
   at System.Data.Entity.Core.Objects.ObjectContext.SaveChangesToStore(SaveOptions options, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction)
   at System.Data.Entity.Infrastructure.DbExecutionStrategy.Execute[TResult](Func`1 operation)
   at System.Data.Entity.Core.Objects.ObjectContext.SaveChangesInternal(SaveOptions options, Boolean executeInExistingTransaction)
   at System.Data.Entity.Internal.InternalContext.SaveChanges()
   at Albatross.Core.Utilities.BasicDataRepository`2.Update(T entity) in c:\DevTFS\AlbatrossEmployers\AlbatrossEmployers_DevTiyuvHeshb\Albatross.Core\Utilities\BasicDataRepository.cs:line 177
****** Inner Exception - START ******
SqlConnection does not support parallel transactions.
   at System.Data.SqlClient.SqlInternalConnection.BeginSqlTransaction(IsolationLevel iso, String transactionName, Boolean shouldReconnect)
   at System.Data.SqlClient.SqlConnection.BeginTransaction(IsolationLevel iso, String transactionName)
   at System.Data.SqlClient.SqlConnection.BeginDbTransaction(IsolationLevel isolationLevel)
   at System.Data.Entity.Infrastructure.Interception.InternalDispatcher`1.Dispatch[TTarget,TInterceptionContext,TResult](TTarget target, Func`3 operation, TInterceptionContext interceptionContext, Action`3 executing, Action`3 executed)
   at System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.BeginTransaction(DbConnection connection, BeginTransactionInterceptionContext interceptionContext)
   at System.Data.Entity.Infrastructure.DbExecutionStrategy.Execute[TResult](Func`1 operation)
   at System.Data.Entity.Core.EntityClient.EntityConnection.BeginDbTransaction(IsolationLevel isolationLevel)
****** Inner Exception - END ******
~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Error - END ~~~~~~~~~~~~~~~~~~~~~~~~~~


The code is pretty simple:

     public virtual T Add(T entity)
        {
            try
            {
                using (U entityContext = new U())
                {
                    T addedEntity = Add(entity, entityContext);
                    entityContext.SaveChanges();
                    return addedEntity;
                }
            }
            catch (DbEntityValidationException e)
            {
                var msg = FormatDbValidationErrors(e);
                throw new Exception(msg);
            }
            catch (Exception ex)
            {
                AmanLog.Logger.Error(ex);
                throw;
            }
        }


 public virtual T Update(T entity)
        {
            try
            {
                using (U entityContext = new U())
                {
                    T existingEntity = Update(entity, entityContext);
                    entityContext.SaveChanges();
                    return existingEntity;
                }
            }
            catch (DbEntityValidationException e)
            {
                var msg = FormatDbValidationErrors(e);
                throw new Exception(msg);
            }
            catch (Exception ex)
            {
                AmanLog.Logger.Error(ex);
                throw;
            }
        }

Answer 1

应用程序使用ThreadPool.QueueUserWorkItem方法处理并发线程中的文件。

不能从两个线程并发使用相同的连接，否则:会发生这种情况。以下任一项：

• 通过单个连接/DB上下文进行同步，使其不能同时使用两次(lock将是实现这一目标的简单方法)
• 使用每个工作项连接/DB上下文，这样就不会共享任何内容。