Question

我想在原子操作中进行check-then-update。我正在使用dbcontext来管理事务。如果记录被另一个线程修改但是没有抛出异常，我期望得到一个异常。任何帮助，将不胜感激。这是我的输出：

Thread-4: Reading...
Thread-5: Reading...
Thread-5: Updating destination 1
Thread-4: Updating destination 1
Thread-4: SaveChanges
Thread-5: SaveChanges

这是我的代码段：

public static void Main(string[] args)
{
    PopulateData();
    (new Thread(UpdateDestination1)).Start();
    (new Thread(UpdateDestination1)).Start();
}

public static void UpdateDestination1()
{
    using (var context1 = new BreakAwayContext())
    {
        Console.WriteLine("Thread-{0}: Reading...", Thread.CurrentThread.ManagedThreadId);
        var d = context1.Destinations.FirstOrDefault();
        Console.WriteLine("Thread-{0}: Updating destination {1}", Thread.CurrentThread.ManagedThreadId, d.DestinationId);
        d.Name = "Thread-" + Thread.CurrentThread.ManagedThreadId;
        try
        {
            context1.SaveChanges();
            Console.WriteLine("Thread-{0}: SaveChanges", Thread.CurrentThread.ManagedThreadId);
        }
        catch (OptimisticConcurrencyException)
        {
            Console.WriteLine("OptimisticConcurrencyException!!!");
            throw;
        }
    }
}

Answer 1

在使用流畅的API（http://msdn.microsoft.com/en-us/data/gg193958.aspx）配置属性时，可以在属性（http://msdn.microsoft.com/en-us/data/jj591617#1.12）或IsConcurrencyToken（）或.IsRowversion上使用ConcurrencyCheck批注。通常，您将在数据库中拥有rowversion列。

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