Question

嗨，我有一个这样的清单：

1 , Ali , 2017 , OK
2 , Ali , 2018 , OK
3 , Ali , 2017 , OK
4 , Ali , 2018 , Good
5 , Ali , 2017 , OK
6 , Ali , 2017 , Good

我希望根据日期加总重复项目，但首先我需要改变ok或good to int number somethings如下：

OK = 10
Good = 5

所以必须输出：

1 , Ali , 2017 , (10+10+10+5 = 35)
2 , Ali , 2018 , (10 + 5 = 15)

所以请帮助我！

Answer 1

给定像

这样的实体

class MyEntity
{
    public int Id;
    public string Name;
    public int Year;
    public string Valuation;
}

以及一些示例数据：

var coll = new[]
{
    new MyEntity { Id = 1, Name = "Ali", Year = 2017, Valuation = "OK" },
    new MyEntity { Id = 2, Name = "Ali", Year = 2018, Valuation = "OK" },
    new MyEntity { Id = 3, Name = "Ali", Year = 2017, Valuation = "OK" },
    new MyEntity { Id = 4, Name = "Ali", Year = 2018, Valuation = "Good" },
    new MyEntity { Id = 5, Name = "Ali", Year = 2017, Valuation = "OK" },
    new MyEntity { Id = 6, Name = "Ali", Year = 2017, Valuation = "Good" },
};

根据@arekzyla的建议，GroupBy和Sum的组合将提供所需的结果。

var grouped = coll.GroupBy(x => new { x.Name, x.Year })
    .Select(x => new
    {
        x.Key.Name,
        x.Key.Year,
        Sum = x.Sum(y => y.Valuation == "OK" ? 10 : y.Valuation == "Good" ? 5 : 0)
    }).ToArray();

注意：我不喜欢各种OK，Good ...如何转换为数字。您应该使用enum和您要编写的特定方法EnumToNumber来转换它们或类似的东西。类似的东西：

public static int EnumToNumber(string value)
{
    switch (value)
    {
        case "OK":
            return 10;

        case "Good":
            return 5;

        default:
            throw new ArgumentOutOfRangeException(nameof(value), value, "Value not recognized");
    }
}

但请注意，我仍然在这里使用string。总和将成为：

Sum = x.Sum(y => EnumToNumber(y.Valuation))

唯一感兴趣的是多字段分组（你没有要求它，但我把它放在代码中）。我按Name和Year分组（new { x.Name, x.Year }是分组键）。

Answer 2

import 'dart:async';

Future sleep1() {
  return new Future.delayed(const Duration(seconds: 1), () => "1");
}

main() {
    sleep1();
    print('This will be logged to the console in the browser.');
}

假设您的课程 ID ，姓名，日期，状态

在linq中重复项目

2 个答案: