c# - 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 IIncludableQueryable<Order, User> ，所以当我执行第二个 Include 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 bool 值，用于选择包含哪些内容和不包含哪些内容。有时它只有两个，但在本例中它有 8 个，这意味着如果我需要 if-else 一切，它可能会产生很多不同的结果。

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> 开始变量(请注意，IIncludableQueryable<T, P> 仍然是 IQueryable<T>，但有额外的 ThenInclude 支持)并使用 ThenInclude而不是嵌套 Select s:

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，自 ThenInclude链不是嵌套的，不需要不同的变量名x , y , z等-单例x或类似的也会做同样的事情。

也是从Include开始正在从根重新启动包含链，非条件赋值如 orders = orders.Include(...)可以组合，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);