Question

如何分组然后在列表中求和下面是我的示例代码：

List<BrandType> brandTypeList = new List<BrandType>();

BrandType brandTypeClass = new BrandType();
brandTypeClass.Amount = 100;
brandTypeClass.Count = 50;
brandTypeClass.Category = "Fish";
brandTypeList.Add(brandTypeClass);

BrandType brandTypeClass2 = new BrandType();
brandTypeClass2.Amount = 100;
brandTypeClass2.Count = 50;
brandTypeClass2.Category = "Fish";
brandTypeList.Add(brandTypeClass2);

BrandType brandTypeClass3 = new BrandType();
brandTypeClass3.Amount = 100;
brandTypeClass3.Count = 50;
brandTypeClass3.Category = "Pork";
brandTypeList.Add(brandTypeClass3);
    brandTypeList.GroupBy(x => new { x.Category }).Select
(x => new { Category = x.Key.Category, 
Amount = x.Sum(z => z.Amount), 
Count = x.Sum(z => z.Count) });

这是它的样子

[0] {Amount = 100, Category = "Pork", Count = 50}
[1] {Amount = 100, Category = "Fish", Count = 50}
[2] {Amount = 100, Category = "Fish", Count = 50}

如何汇总金额和计数，然后按类别分组？我希望结果是

数量= 200，类别=“鱼”，数量= 100

金额= 100，类别=“猪肉”计数= 50

Answer 1

以下代码段将为您工作：

var result = from brand in brandTypeList
            group brand by brand.Category into grp
            select new
            {
                Category = grp.Key,
                Amount = grp.Sum(z => z.Amount),
                Count = grp.Sum(z => z.Count)
            };

这也可以：

var result = brandTypeList.GroupBy(x => x.Category).Select
(y => new {
    Category = y.Key,
    Amount = y.Sum(z => z.Amount),
    Count = y.Sum(z => z.Count)
});

事实证明，您的代码也可以正常工作，可能的问题是您希望对列表进行就地修改，但是linq不会产生副作用，并且将创建新的IEnumerable，并且您需要将结果保存到变量中。

C＃按列表分组，然后按SUM

1 个答案: