Question

考虑以下查询：

var query = from o in this.OrderManager.LoadOrders()
            join s in this.SkuManager.LoadSkus() on o.SKU equals s.SKU
            where o.ORDER_ID == orderId
            let parcelItem = o.RPU != "Y" && o.DROP_SHIP != "Y" && s.TRUCK_SHIP != "T" && o.SKU != "ABC-123" && o.SKU != "XYZ-789" && o.SKU != "JKL-456"
            select new OrderMailLineItem
            {
                OrderId = o.ORDER_ID,
                Sku = s.SKU,
                WarehouseId = s.SITE_ID,
                QualifyingItem = qualifyingItem,
                OversizedItem = parcelItem && (s.DROP_SHIP == null)
            };

我希望能够将let parcelItem = ...行更像!o.SKU.Contains(skuList)，其中：

List<string> skuList = new List<string> { "ABC-123", "XYZ-789", "JKL-456"};

Answer 1

您应该检查SKU是否不在列表中，而不是检查列表是否在SKU中：

let parcelItem = !skuList.Contains(o.SKU)

Answer 2

!skuList.Contains(o.SKU)正是您通常会这样做的。

但如果您愿意，可以编写In运算符：

public static class ExtensionMethods
{
    public static bool In<T>(this T t, params T[] values)
        => values.Contains(t);
}

...

        let parcelItem = o.RPU != "Y" && o.DROP_SHIP != "Y" && s.TRUCK_SHIP != "T" && 
                        !o.SKU.In("ABC-123", "XYZ-789", "JKL-456")

我怀疑它是否会与Linq一起使用SQL。

Answer 3

我不明白为什么这不起作用。除了SKU列表之外，您还需要检查这三个是/否标志。

var skuList = new[] { "ABC-123", "XYZ-789", "JKL-456"};
var query = from o in this.OrderManager.LoadOrders()
        join s in this.SkuManager.LoadSkus() on o.SKU equals s.SKU
        where o.ORDER_ID == orderId
        let parcelItem = o.RPU != "Y" && o.DROP_SHIP != "Y" && s.TRUCK_SHIP != "T" && skuList.Contains(o.SKU)
        select new OrderMailLineItem
        {
            OrderId = o.ORDER_ID,
            Sku = s.SKU,
            WarehouseId = s.SITE_ID,
            QualifyingItem = qualifyingItem,
            OversizedItem = parcelItem && (s.DROP_SHIP == null)
        };

Linq查询Where Contains（）检查字符串列表

3 个答案: