EF Core 条件（添加）包含到 IQueryable

Question

在 EF6 中我习惯这样做：

var orders = GetAllEntities().Include(x => x.Contact.User);
if (includeProducts)
{
    orders = orders.Include(x => x.ProductOrders.Select(y => y.RentStockOrders));
    orders = orders.Include(x => x.ProductOrders.Select(y => y.Product));
    orders = orders.Include(x => x.ProductOrders.Select(y => y.Currency));
    orders = orders.Include(x => x.ProductOrders.Select(y => y.Coupons));
    orders = orders.Include(x => x.AdditionalCosts);
    orders = orders.Include(x => x.Partner);
    orders = orders.Include(x => x.OrderCoupons.Select(y => y.Coupon.Partner));
    if (includeStock)
    {
        orders = orders.Include(x => x.ProductOrders.Select(y => y.RentStockOrders.Select(z => z.Stock)));
    }
}
if (includeInvoices)
{
    orders = orders.Include(x => x.Invoices.Select(y => y.Attachments));
}

在 EF Core 中无法覆盖 IQueryable，因为它更“类型安全”

第一行返回一个IIncludableQueryable<Order, User>，所以当我执行第二个包含时，它想让它变得不同，例如IIncludableQueryable<Ordr,User,ProductOrder>

我主要有一个GetByIdWithCrudRelations，其中包含一组布尔值，用于选择要包含的内容和不包含的内容。有时它只有两个，但在这种情况下它有 8 个，这意味着如果我需要 if-else 一切，它可能会有很多不同的结果。

有人对此有聪明的解决方案吗？

Answer 1

您可以使用完全相同的模式。只需从IQueryable<T> 变量开始（注意IIncludableQueryable<T, P> 仍然是IQueryable<T> 并具有额外的ThenInclude 支持）并使用ThenInclude 而不是嵌套的Selects：

IQueryable<Order> orders = GetAllEntities().Include(x => x.Contact.User);
// or var orders = GetAllEntities().Include(x => x.Contact.User).AsQueryable();
if (includeProducts)
{
    orders = orders.Include(x => x.ProductOrders).ThenInclude(y => y.RentStockOrders);
    orders = orders.Include(x => x.ProductOrders).ThenInclude(y => y.Product);
    orders = orders.Include(x => x.ProductOrders).ThenInclude(y => y.Currency);
    orders = orders.Include(x => x.ProductOrders).ThenInclude(y => y.Coupons);
    orders = orders.Include(x => x.AdditionalCosts);
    orders = orders.Include(x => x.Partner);
    orders = orders.Include(x => x.OrderCoupons).ThenInclude(y => y.Coupon.Partner);
    if (includeStock)
    {
        orders = orders.Include(x => x.ProductOrders).ThenInclude(y => y.RentStockOrders).ThenInclude(z => z.Stock);
    }
}
if (includeInvoices)
{
    orders = orders.Include(x => x.Invoices).ThenInclude(y => y.Attachments);
}

请注意，由于 ThenInclude 链不是嵌套的，因此不需要不同的变量名称 x、y、z 等 - 单个 x 或类似的也可以这样做。

另外，由于Include 是从根目录重新启动包含链，所以可以组合像orders = orders.Include(...) 这样的非条件赋值，例如

orders = orders
    .Include(x => x.ProductOrders).ThenInclude(y => y.RentStockOrders)
    .Include(x => x.ProductOrders).ThenInclude(y => y.Product)
    .Include(x => x.ProductOrders).ThenInclude(y => y.Currency)
    .Include(x => x.ProductOrders).ThenInclude(y => y.Coupons)
    .Include(x => x.AdditionalCosts)
    .Include(x => x.Partner)
    .Include(x => x.OrderCoupons).ThenInclude(y => y.Coupon.Partner);