如何使用linq從另一個列表中的列表中獲取總和作為屬性

Question

我的課程如下。

public class ModelMMaster
{
    public string OrderID { get; set; }
    public bool IsActive { get; set; }
    public List<ModelDetail> _detail { get; set; }
}
public class ModelDetail
{
    public string SKUCode { get; set; }
    public int Quantity { get; set; }
    public double Price { get; set; }
}

我有一個訂單清單

List<ModelMMaster> _listMaster = new List<ModelMMaster>

我想用LINQ在_listMaster上計算Sum(Quantity * Price) 。

我被困在這里。

double _sum =_listMaster.Where(f => f.IsActive == true).Select(f => f._detail)......

如何使用LINQ從_listMaster計算總和（數量*價格）？

Answer 1

您可以通過兩種方式實現它

選項1

double _sum =_listMaster.Where(f => f.IsActive)
                         .Sum(x=>x._detail.Sum(c=>c.Price * c.Quantity));

選項2

double _sum =_listMaster.Where(f => f.IsActive)
                        .Aggregate(0d,(result,item)=>result + item._detail.Sum(x=>x.Price * x.Quantity));

選項3

double _sum =_listMaster.Where(f => f.IsActive)
                        .SelectMany(x=>x._detail)
                        .Sum(x=>x.Price * x.Quantity);

Answer 2

        List<ModelMMaster> _listMaster = new List<ModelMMaster>();
        List<ModelDetail> _listDetail = new List<ModelDetail>();

        _listDetail.Add(new ModelDetail { SKUCode = "SKUCode-1", Quantity = 1, Price = 1 });
        _listMaster.Add(new ModelMMaster { OrderID = "OrderID-1", IsActive = true, _detail = _listDetail });

        _listDetail = new List<ModelDetail>();
        _listDetail.Add(new ModelDetail { SKUCode = "SKUCode-2", Quantity = 2, Price = 2 });
        _listDetail.Add(new ModelDetail { SKUCode = "SKUCode-3", Quantity = 3, Price = 3 });
        _listMaster.Add(new ModelMMaster { OrderID = "OrderID-2", IsActive = true, _detail = _listDetail });

        var totalSum = _listMaster.Where(t=>t.IsActive).SelectMany(t => t._detail).Sum(t => t.Quantity * t.Price);