阅读带有linq-skip重复id的Excel表格

Question

In following excel file, I need to read rows as Student class which define single object for the unique ID and then get all exams associated with this student.

If I used the following code I generate number of students equal to number of rows and without specifying exams list for each object student.

IQueryable<Student> Students_var;

var  excel = new ExcelQueryFactory(fileName_global1);
excel.AddMapping<Student>(x => x.ID, "STU_NO");
Students_var = from c in excel.Worksheet<Student>("Stu_Schedule")
                select c;
List<Student> StudentList_c = Students_var.ToList();

Answer 1

I've simplified a your questions in order to have a working unit test.

I'm creating the values locally instead of reading it from an excel file.

in the values that I'm creating I have 3 items but only 2 students so I'm verifying that the linq query returns always 2 records.

you can see in the below code how to group your items.

    [Test]
    public void LinqSelect_MultipleRowsWithTheSameId_RemoveDuplicatedRecords()
    {
        var excel = new [] {new Student() {ID = 1,Exam = 1}, new Student() { ID = 1, Exam = 2 }, new Student() { ID = 2, Exam = 1 } };
        IEnumerable<IGrouping<int,Student>> Students_var = from c in excel
                           group c by c.ID into newExcel
                       select newExcel;
        Assert.AreEqual(2, Students_var.ToList().Count);
    }

    public class Student
    {
        public int ID { get; set; }
        public int Exam { get; set; }
    }

Answer 2

You can group by the Student ID then add each exam to the Student Object.

var grouped  = StudentList_c.GroupBy(x => x.ID).Select(x => new Student
        {
            ID = x.Key,
            Exam = x.SelectMany(z=> z.Exam).ToList()
        }).ToList();


public class Student
{
    public int ID { get; set; }
    public List<int> Exam { get; set; }
}

Answer 3

var rows = excel.Worksheet<Student>("Stu_Schedule").ToList();

var groupedStudents = rows.GroupBy(y=>y.Id)
                          .Select(x => new Student
    {
        ID = x.Key,
        Exam = x.SelectMany(z=> z.Exam).ToList()
    }).ToList();