public class CreateOrderCommandHandler : IRequestHandler<CreateOrderCommand, int>
{
    public async Task<int> Handle(CreateOrderCommand request, CancellationToken ct)
    {
        using var transaction = await _dbContext.Database.BeginTransactionAsync(_capPublisher);
        
        try
        {
            // ===== 核心业务：写在一起，清晰可见 =====
            
            // 1. 检查库存（核心，必须同步）
            var stock = await _inventoryService.CheckStockAsync(request.ProductName);
            if (stock < request.Quantity)
                throw new BusinessException("库存不足");
            
            // 2. 计算价格（核心，必须同步）
            var price = await _pricingService.CalculateAsync(request);
            
            // 3. 创建订单（核心）
            var order = new Order
            {
                ProductName = request.ProductName,
                Quantity = request.Quantity,
                TotalPrice = price
            };
            _dbContext.Orders.Add(order);
            
            // 4. 扣减库存（核心，必须在同一事务）
            await _inventoryService.DecreaseStockAsync(request.ProductName, request.Quantity);
            
            await _dbContext.SaveChangesAsync(ct);
            
            // ===== 非核心业务：通过 CAP 异步解耦 =====
            // （邮件、短信、推送、统计等，失败了也不影响订单创建）
            await _capPublisher.PublishAsync("order.created", new
            {
                OrderId = order.Id,
                ProductName = order.ProductName,
                UserEmail = request.UserEmail
            }, cancellationToken: ct);
            
            await transaction.CommitAsync(ct);
            
            return order.Id;
        }
        catch
        {
            await transaction.RollbackAsync(ct);
            throw;
        }
    }
}

// 非核心业务通过 CAP 订阅处理
public class OrderEventSubscriber : ICapSubscribe
{
    [CapSubscribe("order.created")]
    public async Task HandleOrderCreated(OrderCreatedEvent @event)
    {
        // 这些操作失败了不影响订单创建
        await _emailService.SendAsync(@event.UserEmail, "订单创建成功");
        await _smsService.SendAsync(@event.UserPhone, "订单创建成功");
        await _statisticsService.UpdateAsync(@event.OrderId);
    }
}