Question

我有一个看起来像这样的列表

List<custom> this_list = new List<custom>();

this_list.Add(new custom()
{
  key = male,
  value = 50
});

this_list.Add(new custom()
{
  key = female,
  value = 90
});

this_list.Add(new custom()
{
  key = male,
  value = 5
});

我如何评估此列表，以便确定有55名男性和90名女性？另外，假设我的密钥集非常大，手动定义男性或女性或其他密钥效率低下。如何创建包含合计总计和唯一键的新列表？

感谢您的帮助和关注！

Answer 1

您可以在性别上使用GroupBy进行分组：

var query = this_list.GroupBy(x=> x.key)
                     .Select(g=> new {Gender = g.Key, Count = g.Sum(x=>x.value)});

foreach(var result in query)
{
   Console.WriteLine("{0} : {1}", result.Gender, result.Count);
}

Answer 2

var results = from c in this_list
              group c by c.key into g
              select new custom(g.Key, g.Sum(x=>x.value));

//results now has two elements of the original "custom" type; 
//one male with a count of 55, one female with a count 90

Answer 3

from c in this_list
group c.value by c.key into g
select new custom { key = g.Key, value = g.Sum() }

Answer 4

LINQ！

this_list.Where(c => c.key == male).Select(c => c.value).Sum();

Answer 5

更新：我误解了这个问题。我喜欢Sam我的回答：

this_list.Where(c => c.key == male).Select(c => c.value).Sum();

这些不起作用：

var maleCount = this_list.Count(item => item.key == male);
var femaleCount = this_list.Count(item => item.key == female);

如何在List <t>中使用键值相同的总值</t>

5 个答案: