Objective
In this article, I am going to show, how we could achieve grouping in LINQ to object
I have created two classes for my explanation purpose. Student class is having details of students and Hostel class is having details of hostel. Both classes are having a properties HostelNumber common. I will be using this property to perform join operations in later articles. Both classes are as below.
Student.cs
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5
6 namespace LINQtoOBJECT1
7 {
8 public class Student
9 {
10
11 public int RollNumber { get; set; }
12 public string Name { get; set; }
13 public int Section { get; set; }
14 public int HostelNumber { get; set; }
15 }
16 }
17
Hostel.cs
3 using System.Linq;
4 using System.Text;
5
6 namespace LINQtoOBJECT1
7 {
8 public class Hostel
9 {
10
11 public int HostelNumber { get; set; }
12 public int NumberofRooms { get; set; }
13 }
14 }
15
To create collection of students and hostels, I am creating two static functions.
Function to return collection of students.
1 static List<Student> GetStudents()
2 {
3 List<Student> students = new List<Student>
4 {
5 new Student() { RollNumber = 1,Name =“Alex “ , Section = 1 ,HostelNumber=1 },
6 new Student() { RollNumber = 2,Name =“Jonty “ , Section = 2 ,HostelNumber=2 },
7 new Student() { RollNumber = 3,Name =“Samba “ , Section = 3 ,HostelNumber=1 },
8 new Student() { RollNumber = 4,Name =“Donald “ , Section = 3 ,HostelNumber=2 },
9 new Student() { RollNumber = 5,Name =“Kristen “ , Section = 2 ,HostelNumber=1 },
10 new Student() { RollNumber = 6,Name =“Mark “ , Section = 1 ,HostelNumber=2},
11 new Student() { RollNumber = 7,Name =“Gibbs “ , Section = 1 ,HostelNumber=1 },
12 new Student() { RollNumber = 8,Name =“Peterson “ , Section = 2 ,HostelNumber=2 },
13 new Student() { RollNumber = 9,Name =“collingwood “ , Section = 3 ,HostelNumber=1 },
14 new Student() { RollNumber = 10,Name =“Brian “ , Section = 3 ,HostelNumber=2 }
15
16 };
17
18 return students;
19
20 }
Function to return collection of hostels
1 static List<Hostel> GetHostel()
2 {
3 List<Hostel> hostels = new List<Hostel>
4 {
5
6 new Hostel(){HostelNumber=1 ,NumberofRooms = 100},
7 new Hostel(){HostelNumber= 2 ,NumberofRooms = 200}
8 };
9 return hostels;
10 }
Now have a look on both codes below, one is using LINQ and other is using LOOP to retrieve data from the list and print.
Note: I will be using above two classes and functions for my entire sample below.
Grouping in LINQ
Syntax of Groupby
Var result = FROM selectVariable IN dataSourceorList GROUPBY selectVariable.variable INTO RANGEVARIABLE Select new { };
Grouping by a single property
1 class Program
2 {
3 static void Main(string[] args)
4 {
5
6
7 List<Student> lstStudents = GetStudents();
8 var lstStudentName = from r in lstStudents
9 group r by r.HostelNumber into rngStudent
10 select new
11 {
12 HostelID = rngStudent.Key,
13 Students = rngStudent
14 };
15
16 foreach (var name in lstStudentName)
17 {
18 Console.WriteLine(name.HostelID);
19 foreach (Student s in name.Students)
20 {
21 Console.WriteLine(s.RollNumber + s.Name);
22 }
23 }
24 Console.ReadKey();
25
26 }
27
Explanation
- I am grouping on property hostel number.
- rngStudent is range variable in which ; I am putting the intermediate result.
- I am selecting the result in as anonymous type.
- While printing the result , first I am printing the key of group by and then retrieving the object in foreach.
1 foreach (var name in lstStudentName)
2 {
3 Console.WriteLine(name.HostelID);
4 foreach (Student s in name.Students)
5 {
6 Console.WriteLine(s.RollNumber + s.Name);
7 }
8 }
Output
Accessing the Group object
1 foreach (var name in lstStudentName)
2 {
3 Console.WriteLine(name.HostelID);
4 foreach (Student s in name.Students)
5 {
6 Console.WriteLine(s.RollNumber + s.Name);
7 }
8 }
If you see the above loop , first I am looping the key for the group by clause and then , I am looping through IEnumerable LINQ object. This object is containing the real result.
Conclusion
In this article, I have discussed GROUPING in LINQ to OBJECT. Thanks for reading.
Dhananjay Kumar 
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