如何首先使用EF 5.0代码启用并发检查？

Question

我想在一个原子操作中做一个检查-然后-更新。我使用dbcontext来管理事务。如果记录被另一个线程修改了，我希望得到一个异常，但没有抛出异常。任何帮助都将不胜感激。下面是我的输出：

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

下面是我的代码片段：

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

使用fluent API ( http://msdn.microsoft.com/en-us/data/jj591617#1.12)配置属性时，可以在属性上使用ConcurrencyCheck批注( http://msdn.microsoft.com/en-us/data/gg193958.aspx )、IsConcurrencyToken()或.IsRowversion。通常，数据库中会有一个rowversion列。