在IEnumerable中定义具有特定ID的项目

Question

CustomClass{
int ID;
int numberToSum;
float numToAverage;
}


IEnumerable<CustomClass> results = MethodToPopulateIEnumerable();
List<int> listOfIDs = MethodToGetListOfIDs();

我想用这些来做,就是拿我的IEnumberable<CustomClass>并选择ID所在的那些List<int> listOfIDs,然后我希望将它的numberToSum值加起来并将其保存在一个变量中并获得numToAverage属性的平均值并将其保存在变量.

这样做最优雅的方法是什么？

Answer 1

我想你正在寻找这样的东西:

IEnumerable<CustomClass> results = MethodToPopulateIEnumerable();
List<int> listOfIDs = MethodToGetListOfIDs();

查询语法

 var query = from c in results
             where listOfIds.Any(x => x == c.ID)
             select c;

方法语法

var query = results.Where(c => listOfIds.Any(x => x == c.ID));

计算

int numberToSum = query.Sum(x => x.numberToSum);
float numToAverage = query.Average(x => x.numToAverage);

这将由其他成员allievate一些表演的担忧,但仍允许查询是另一种替代方法LINQ到什么友好(linq-to-entities,linq-to-sql):

var calculations = (from c in results
                   where listOfIds.Any(x => x == c.ID)
                   group c by 1 into g
                   select new {
                     numberToSum = g.Sum(x => x.numberToSum ),
                     numToAverage = g.Average(x => x.numToAverage),                
                   }).FirstOrDefault();