将所有相同主题的TestScore求和并将总值赋给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},
};
有没有类似的东西？
foreach (TestScore ts in testScores)
{
ts.SUBTOTAL = Sum(testScores.SUBJECT == ts.SUBJECT);
}
前提是您SUBJECT在TestScores定义中声明了一个属性，这是您需要的：
var grouped = testScores.GroupBy(ts=>ts.SUBJECT)
.Select(g => new {SUBJECT = g.Key,
Sum = g.Sum(ts=> ts.SCORE)});
结果将是IEnumerable匿名类型的，每个实例将具有SUBJECT和Sum成员。
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