列出<class>如何获得小计

Question

总结所有同一个SUBJECT的TestScore并将总值放到每个实例的最简单方法是什么？

public class TestScore
{
    public int ID { get; set; }
    public int SUBJECT { get; set; }
    public int SCORE { get; set; }
    public int SUBTOTAL { get; set; }
}

List<TestScore> testScores = new List<TestScore>{
    new TestScore{ ID = 0, SUBJECT = "MATH", SCORE = 10},
    new TestScore{ ID = 1, SUBJECT = "MATH", SCORE = 20},
    new TestScore{ ID = 2, SUBJECT = "ENGLISH", SCORE = 10},
    new TestScore{ ID = 3, SUBJECT = "ENGLISH", SCORE = 20},
    new TestScore{ ID = 4, SUBJECT = "ENGLISH", SCORE = 30},    
};

有类似的东西吗？

foreach (TestScore ts in testScores)
{
    ts.SUBTOTAL = Sum(testScores.SUBJECT == ts.SUBJECT);
}

Answer 1

如果您SUBJECT在TestScores定义中声明了一个属性,那么这就是您所需要的:

var grouped = testScores.GroupBy(ts=>ts.SUBJECT)
                        .Select(g => new {SUBJECT = g.Key, 
                                          Sum = g.Sum(ts=> ts.SCORE)});

结果将是一个IEnumerable匿名类型,其中每个实例都有SUBJECT和Sum成员.