EF linq模拟中的临时创建表中的异常

Question

我已经使用假数据库上下文实现了EF测试。以下是我的sql查询，

     flatLicenseOrderId = (from users in this.CustomerEntities.UserMappers
                                              where users.CompanyId == CompanyId && users.IsActive
                                              join order in this.CustomerEntities.Orders on users.customerid equals order.customerid into orderDetails
                                              from customerOrder in orderDetails.DefaultIfEmpty()
                                              join license in this.CustomerEntities.License on users.Customerid equals license.Customerid into licenseDetails
                                              from customerLicense in licenseDetails.DefaultIfEmpty()
                                              from orderdetails in this.CustomerEntities.OrderDetails
                                              where (customerOrder.OrderId == orderdetails.OrderId || customerLicense.OrderId == orderdetails.OrderId) 
                                              select orderdetails.OrderId).Distinct().ToList();

下面是我的Mocking背景，

     public static CustomerEntities GetOrderDetails()
            {
                var mockData = new Mock<CustomerEntities>();                

                var users = new FakeDbSet<UserMapper>
                {
                    new UserMapper { CompanyId = 27835, IsActive = true, CustomerId = 956980 },
                    new UserMapper { CompanyId = 148150, IsActive = true, CustomerId = 1039733 }
                };

                mockData.Setup(m => m.UserMappers).Returns(users);

                var order = new FakeDbSet<Orders>
                {
                    new Orders { CustomerId  = 956980, OrderId = 401789 },
                    new Orders { CustomerId = 956980, OrderId = 426192 }                   
                };

                mockData.Setup(m => m.Orders).Returns(order);    

                var license = new FakeDbSet<License>
                {
                   new License { Customerid = 956980, OrderId = 401789 },
                   new License { Customerid = 1039733, OrderId = 423132 }
                };

                mockData.Setup(m => m.License).Returns(license);

                var orderdetails = new FakeDbSet<OrderDetails>
                {
                    new OrderDetails { OrderId = 401789, ProductID = 7703 },
                    new OrderDetails { OrderId = 401789, ProductID = 7002 }                   
                };

                mockData.Setup(m => m.OrderDetails).Returns(orderdetails);

                return mockData.Object;
            }

在使用所有使用的表中存在的值模拟此代码时，模拟工作正常。但是如果该值不在Orders表中，则会出现以下错误：

Message: Object reference not set to an instance of an object.

Source: Anonymously Hosted DynamicMethods Assembly

示例：对于customerid = 956980，模拟工作正常，但对于另一个customerid = 1039733，则产生异常，因为客户在Order表中没有条目。

有人可以帮忙，如何处理这类案件的嘲笑？

Answer 1

试试这个。在数据库操作的情况下它可能会失败，但对于模型，它会因为concise操作而做得很好。

flatLicenseOrderId = (from users in this.CustomerEntities.UserMappers
                                        .Where(x=>x.CompanyId==CompanyId && x.IsActive)
                      join order in this.CustomerEntities.Orders 
                           on users.customerid equals order.customerid 
                      into orderDetails
                      from customerOrder in orderDetails.DefaultIfEmpty()
                      join orderdetails in this.CustomerEntities.OrderDetails
                      on customerOrder?.OrderId equals orderdetails.OrderId
                      select new{users.customerid,orderdetails.OrderId})
                     .Distinct().ToList();