c# - 如何将外部参数包含到列表中

Question

我正在从不同的类中分别获取购物车数量，如下所示。我想从列表中包含的数量中减少购物车数量。那么如何将其包含在我的查询中。任何人都请建议我。

//int quantityinshoppingcart = classes.ShoppingCart.checkingQuantity(CustomerId,ItemId);


//Binds the data to the repeater control
rptcontrol.DataSource =   from p in l_List
      select new
      {
        ItemId = p.ItemId,
        ItemName = p.ItemName,
        Quantity = p.Quantity,                                                        
        //I want quantity as (Quantity = p.quantity - quantityinshoppingcart),
      };
      rptcontrol.DataBind();  

Answer 1

您可以在查询中使用 let 关键字:

var q = from p in l_List
        let quantityInShoppingCart = MethodThatGetsThisQuantity(p.ItemId)
        let computedQuantity = p.Quantity - quantityInShoppingCart
        select new { ItemId = p.ItemId,
                     ItemName = p.ItemName,
                     Quantity = computedQuantity 
                   };