c# - 在异步/等待代码中重新分配 Transaction.Current 时上下文丢失

Question

重新分配 Transaction.Current 时，我似乎失去了 TransactionScope 的原始 TransactionScopeAsyncFlowOption 行为。第二个 await 之后的代码失去了它的 Transaction.Current 值。

示例代码(Linqpad):

async Task Main()
{
    Thread.CurrentThread.ManagedThreadId.Dump("before await");
    var scope = new TransactionScope(TransactionScopeOption.Required, TransactionScopeAsyncFlowOption.Enabled);
    var transaction = Transaction.Current;

    await Task.Delay(1000).ConfigureAwait(false);

    Thread.CurrentThread.ManagedThreadId.Dump("after first await");
    Transaction.Current = transaction;
    Transaction.Current.Dump(); // not null

    await Task.Delay(1000).ConfigureAwait(false);

    Thread.CurrentThread.ManagedThreadId.Dump("after second await");
    Transaction.Current.Dump(); // is null :/
}

我know我应该在 TransactionScope 上使用 using 语句，而不是重新分配环境事务，但是由于某些原因，不可能这样做。我很好奇上面代码片段的行为原因，想知道是否有办法保持原始的 TransactionScopeAsyncFlowOption 行为。

Answer 1

我通过将 Transaction 对象包装在另一个启用了 TransactionScopeAsyncFlowOption 的 TransactionScope 中设法解决了这个问题:

async Task Main()
{
    var scope = new TransactionScope(TransactionScopeOption.Required, TransactionScopeAsyncFlowOption.Enabled);
    var transaction = Transaction.Current;

    await Task.Delay(1000);

    Transaction.Current = transaction;
    Debug.Assert(Transaction.Current != null); // not null

    await Task.Delay(1000);

    Debug.Assert(Transaction.Current == null); // is null :/

    using (var innerScope = new TransactionScope(transaction, TransactionScopeAsyncFlowOption.Enabled))
    {
        // Transaction.Current state is kept across async continuations
        Debug.Assert(Transaction.Current != null); // not null
        await Task.Delay(10);
        Debug.Assert(Transaction.Current != null); // not null
        innerScope.Complete();
    }
}