Question

我不是Linq的专业人士，而是试图理解。如何用C＃

编写这段代码（用VB编写）

Dim x =来自db.YourClass _中的p

其中p.fl1 = cn1且p.f12 = cn2

选择_

sum1 = x.Sum（Function（y）y.fl1），_

sum2 = x.Sum（函数（y）y.fl2），_

sum3 = x.Sum（函数（y）y.fl3）

我想要实现的是这个，

选择sum（fl1），sum（fl2），sum（fl3）

其中fl1 = cn1且fl2 = cn2

The above sample found here

Answer 1

var x =
    from p in db.YourClass
    where p.fl1 == cn1 && p.fl2 == cn2
    select p;


var sum1 = x.Sum(y => t.fl1);
var sum2 = x.Sum(y => t.fl2);
var sum3 = x.Sum(y => t.fl3);

Answer 2

var x = from p in db.YourClass 
        where p.fl1 == cn1 && p.f12 == cn2
        select p;

  var sum1 = x.Sum(y=>y.fl1), 

  var sum2 = x.Sum(y=>y.fl2), 

  var sum3 = x.Sum(y=>y.fl3)

编辑：在一个查询中，我认为这可以很快地运作：

var x = (from p in db.YourClass 

        select new 
        {
         s1 = db.YourClass.Where(y=> y.fl1 == cn1 && y.f12 == cn2).Sum(y=>y.fl1),
         s2 = db.YourClass.Where(y=> y.fl1 == cn1 && y.f12 == cn2).Sum(y=>y.fl2),
         s3 = db.YourClass.Where(y=> y.fl1 == cn1 && y.f12 == cn2).Sum(y=>y.fl3)
        }).First();

 int sum1 = x.s1, sum2 = x.s2, sum3 = x.s3;

Answer 3

你可以使用lambda表达式，

public class Sums
{
   public int Sum1{get;set;}
   public int Sum2{get;set;}
   public int Sum3{get;set;}
}

var list = db.YourClass.Where(x=>x.fl1==cn1 && x.f12==cn2).Select(y => 
                                new Sums{ 
                                    Sum1 = y.Sum(z=>z.fl1),
                                    Sum2 = y.Sum(z=>z.fl2),
                                    Sum3 = y.Sum(z=>z.fl3)
                                }).ToList();

如何用C＃Linq编写这个

3 个答案: