c# - 多个独立数据库事务的并发问题？

Question

您将如何解决以下代码的并发问题？在这个示例中，我们想知道用户身份验证失败的原因。问题是这段代码对数据库进行了两次单独的调用，但我们希望整个方法发生在一个概念性事务中。具体来说，我们对 isolation 感兴趣.在我们确定身份验证失败的原因之前，我们不希望执行此方法期间的并发写入影响我们的读取。

我想到了一些解决方案:Thread Locking , TransactionScope和 Optimistic Locking .我真的很喜欢乐观锁定的想法，因为我认为冲突可能很少见，但是 .NET 中没有内置任何东西可以做到这一点，对吧？

此外 - 在这种情况下，这真的值得关注吗？像这样的并发问题什么时候需要考虑，什么时候不需要？实现解决方案需要考虑什么？表现？锁定时间？发生冲突的可能性有多大？

编辑:在查看 Aristos 的回答后，我认为我真正想要的是 Authenticate 方法的某种“snapshot”隔离级别。

public MembershipStatus Authenticate(string username, string password)
    {
        MembershipUser user = Membership.GetUser(username);
        if (user == null)
        {
            // user did not exist as of Membership.GetUser
            return MembershipStatus.InvalidUsername;
        }

        if (user.IsLockedOut)
        {
            // user was locked out as of Membership.GetUser
            return MembershipStatus.AccountLockedOut;
        }

        if (Membership.ValidateUser(username, password))
        {
            // user was valid as of Membership.ValidateUser
            return MembershipStatus.Valid;
        }

        // user was not valid as of Membership.ValidateUser BUT we don't really
        // know why because we don't have ISOLATION.  The user's status may have changed
        // between the call to Membership.GetUser and Membership.ValidateUser.
        return MembershipStatus.InvalidPassword;
    }

Answer 1

根据我的阅读 here和 here ，它似乎是一个 System.Transactions.TransactionScope 包装你的整个方法应该自动在一个公共(public)事务中登记你的数据库调用，从而在整个事务范围内实现事务安全。

你想做这样的事情:

public MembershipStatus Authenticate(string username, string password)
{
    using (TransactionScope scope = new TransactionScope(TransactionScopeOption.Required, new TransactionOptions { IsolationLevel = IsolationLevel.Snapshot }))
    {
    MembershipUser user = Membership.GetUser(username);
        if (user == null)
        {
            // user did not exist as of Membership.GetUser
            return MembershipStatus.InvalidUsername;
        }

        if (user.IsLockedOut)
        {
            // user was locked out as of Membership.GetUser
            return MembershipStatus.AccountLockedOut;
        }

        if (Membership.ValidateUser(username, password))
        {
            // user was valid as of Membership.ValidateUser
            return MembershipStatus.Valid;
        }

        // user was not valid as of Membership.ValidateUser BUT we don't really
        // know why because we don't have ISOLATION.  The user's status may have changed
        // between the call to Membership.GetUser and Membership.ValidateUser.
        return MembershipStatus.InvalidPassword;
    }
}