Entity Framework with NOLOCK

/// <summary>
    /// 类似SqlServer nolock 查询扩展
    /// Like SqlServer Nolock
    /// </summary>
    public static class NoLockQuery
    {
        public static List<T> ToListReadUncommitted<T>(this IQueryable<T> query)
        {
            using (var scope = new TransactionScope(
                TransactionScopeOption.Required,
                new TransactionOptions()
                {
                    IsolationLevel = System.Transactions.IsolationLevel.ReadUncommitted
                }))
            {
                List<T> toReturn = query.ToList();
                scope.Complete();
                return toReturn;
            }
        }

        public static int CountReadUncommitted<T>(this IQueryable<T> query)
        {
            using (var scope = new TransactionScope(
                TransactionScopeOption.Required,
                new TransactionOptions()
                {
                    IsolationLevel = System.Transactions.IsolationLevel.ReadUncommitted
                }))
            {
                int toReturn = query.Count();
                scope.Complete();
                return toReturn;
            }
        }

        public static async Task<List<T>> ToListReadUncommittedAsync<T>(this IQueryable<T> query)
        {
            using (var scope = new TransactionScope(
                TransactionScopeOption.Required,
                new TransactionOptions()
                {
                    IsolationLevel = System.Transactions.IsolationLevel.ReadUncommitted
                },
                  TransactionScopeAsyncFlowOption.Enabled
                ))
            {
                List<T> toReturn = await query.ToListAsync();
                scope.Complete();
                return toReturn;
            }
        }

        public static async Task<int> CountReadUncommittedAsync<T>(this IQueryable<T> query)
        {
            using (var scope = new TransactionScope(
                TransactionScopeOption.Required,
                new TransactionOptions()
                {
                    IsolationLevel = System.Transactions.IsolationLevel.ReadUncommitted
                },
                 TransactionScopeAsyncFlowOption.Enabled
                ))
            {
                int toReturn = await query.CountAsync();
                scope.Complete();
                return toReturn;
            }
        }
    }

项目中使用EntityFramework，可以使用下面这段代码进行nolock查询：需要添加System.Transactions程序集的引用

如果封装的话，执行的时候，就需要传一个代码片段进去，委托在这种情况就派上用场了，我们可以使用委托来改进一下，也就是查询数据库时候的逻辑代码代由委托传递进去。

public static void NoLockInvokeDB(Action action)
        {
            var transactionOptions = new System.Transactions.TransactionOptions();
            transactionOptions.IsolationLevel = System.Transactions.IsolationLevel.ReadUncommitted;
            using (var transactionScope = new System.Transactions.TransactionScope(System.Transactions.TransactionScopeOption.Required, transactionOptions))
            {
                try
                {
                    action();
                }
                finally
                {
                    transactionScope.Complete();
                }
            }
        }

调用：

NoLockInvokeDB(() =>
{
   using (var db = new TicketDB())
   {
      lst = db.User.ToList();
   }
});