我如何使用Linq进行多个属性的求和

问题描述

我有同样的问题.我想为学生计算分数.我做了:

I has same a problem. which I want caculator score for student. I done:

var cosrse = from ssh in cn.DB.ScoreSheets 
                            where ssh.CourseID == CourseID 
                            select new 
                           { 
                              Student = ssh.Student.LastName +" "+ ssh.Student.FirstName, 
                              ssh.Student.StudentID, Assignment = ssh.Assignment,
                              Project = ssh.Project,
                              ssh.Midterm,
                              ssh.Endterm,
                              ssh.Practice,
                              FinalMatch = ssh.Midterm * 0.2 + ssh.Project * 0.3 + ssh.Endterm * 0.5 //  new a propety FinalMatch 
                           };

我想添加列 FinalMatch 并分配

I want to add column FinalMatch and assign

ssh.Midterm * 0.2 + ssh.Project * 0.3 + ssh.Endterm * 0.5 

，但我没有得到任何结果

, But I don''t get any result

推荐答案

private void button1_Click(object sender, EventArgs e)
        {
        List<Student> list = new List<Student>();
        list.Add(new Student(10, 11));
        list.Add(new Student(20, 21));
        list.Add(new Student(30, 31));
        list.Add(new Student(40, 41));
        var c = from s in list
                select new { A = s.A, B = s.B, sum = s.A + s.B };
        foreach (var s in c)
            {
            Console.WriteLine("{0}:{1}+{2}", s.sum, s.A, s.B);
            }
        }
    }
public class Student
    {
    public int A { get; set; }
    public int B { get; set; }
    public Student(int a, int b)
        {
        A = a;
        B = b;
        }
    }

而我得到了期望的结果:

And I get what I would expect:

21:10+11
41:20+21
61:30+31
81:40+41

因此，当您说:但是我没有任何结果"时，您会得到什么?可能是您的ssh.CourseID == CourseID条件没有选择任何记录吗?

So when you say: "But I don''t get any result" what do you get? Could it be that your ssh.CourseID == CourseID condition is selecting no records?

var result = from c in db.scoresheets
                        where c.CourseID == 1
                        select new { Mid = c.MidTerm, Last = c.LastTerm, sum1 =( c.MidTerm == null ? 0 : c.MidTerm )+ (c.LastTerm == null ? 0 : c.LastTerm) };

这篇关于我如何使用Linq进行多个属性的求和的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！