c# - 为什么内部 TransactionScope 的 IsolationLevel 不能不同，而 SQL 事务可以不同？

Question

更改数据库事务中的隔离级别是可以的，包括将一个事务加入到已经运行的事务中的情况。从现在开始，您只需更改处理锁的方式即可。使用 SQL Server，这运行没有问题:

begin transaction 
set transaction isolation level serializable;
select * from FooTable;

set transaction isolation level read committed;
select * from FooTable;

begin transaction
set transaction isolation level serializable;
select * from FooTable;
--transaction_isolation_level can be observed as 4 (serializable)

但是，当使用 .NET TransactionScope 在上述 SQL Server 中创建事务时(C#、xUnit):

[Theory]
[AutoFixtureMagicToGetParameterInstances]
void ZmenaIzolacniUrovneVedeKVyjimce(IFooDao sut, Foo foo)
{
    var tranOpts = new TransactionOptions()
    {
        IsolationLevel = IsolationLevel.Serializable,
        Timeout = TimeSpan.FromSeconds(60)
    };
    var tranOpts2 = new TransactionOptions()
    {
        IsolationLevel = IsolationLevel.ReadCommitted,
        Timeout = TimeSpan.FromSeconds(60)
    };
    using (var transactionScope = new TransactionScope(TransactionScopeOption.Required, tranOpts))
    {
        sut.SelectFoos();
        using (var transactionScope2 = new TransactionScope(TransactionScopeOption.Required, tranOpts2))
        {
            sut.SelectFoos();
        }
    }
}

导致异常:

System.ArgumentException : The transaction specified for TransactionScope has a different IsolationLevel than the value requested for the scope.
 Parameter name: transactionOptions.IsolationLevel

为什么 TransactionScope 的设计者认为有必要立即抛出异常？

我希望至少只要只涉及数据库资源，行为就会相同。是否有关于 TransactionScope 的内容我遗漏了，或者仅仅是因为无法保证所有可能的征用资源的合理行为？

Answer 1

如此处评论所述Inner TransactionScope with different IsolationLevel, how can it be achieved?

TransactionScope is not limited to use with SQL Server, it can allow distributed transactions across processes/systems. So it is stricter than what SQL Server allows, likely to simplify the complexity of ensuring consistency across the systems than support distributed transactions. – AaronLS

所以答案基本上似乎可以归结为“TransactionScope 可能 在它的板 block 上有更多的方式而不仅仅是数据库事务，因此它禁止像更改隔离级别这样的复杂性”。