Question

我有这个查询

    var test = context.Assignments
        .Include(a => a.Customer)
        .Include(a => a.Subscriptions)
        .Select(a => new AssignmentWithSubscriptionCount { SubscriptionCount = a.Subscriptions.Count(), Assignment = a })
        .ToList();

    var name = test.First().Assignment.Customer.Name;

它急于加载客户，我在stackoverflow上看到类似的问题，看起来你不能使用包含的投影。但是我没有找到解决问题的方法..任何人？

编辑：这是一个令人满意的投影加载，它比上面的例子更复杂，所以我不能理解我的生活是错的，谢谢。

    var test = context.PublicationStateGroups
        .Include(p => p.PublicationStates.Select(ps => ps.AllowedPublicationStateActions.Select(aps => aps.PublicationStateAction)))
        .Select(psg => new StateAndGroupInfo
        {
            ShowReport = psg.PublicationStates.Any(p => p.PublicationStateReportTypeId.HasValue),
            Actions = psg.PublicationStates.SelectMany(state => state.AllowedPublicationStateActions)
                .Select(a => a.PublicationStateAction)
                .Distinct()
        }).ToList();

    var eagerTest = test.First().Actions.First().Name;

Answer 1

这是by design。 Include不适用于包含投影或自定义联接的方案。

Answer 2

将客户添加到您的预测中：

var test = context.Assignments
    .Select(a => new AssignmentWithSubscriptionCount
    {
        SubscriptionCount = a.Subscriptions.Count(),
        Assignment = a,
        Customer = a.Customer
    });

var name = test.First().Customer.Name;

EF上下文可能会确保Assignment.Customer自动填充。

修改

如果您不想或不能更改AssignmentWithSubscriptionCount类，您也可以投影到匿名类型，然后将结果复制到内存中：

var test = context.Assignments .Select(a => new { SubscriptionCount = a.Subscriptions.Count(), Assignment = a, Customer = a.Customer }); test.ToList() // executes query .Select(o => { o.Assignment.Customer = o.Customer; return new AssignmentWithSubscriptionCount { SubscriptionCount = o.SubscriptionCount, Assignment = o.Assignment } });

另一种选择是明确加载（每个加载Assignment需要一次额外的往返）。

包含投影不起作用

2 个答案: