Join Operators in LINQ Tutorial

Joining refers to an operation in which data sources with difficult to follow relationships with each other in a direct way are targeted.

Show Examples

Operator
Description
C# Query Expression Syntax
VB Query Expression Syntax
Join
The operator join two sequences on basis of matching keys
join … in … on … equals …
From x In …, y In … Where x.a = y.a
GroupJoin
Join two sequences and group the matching elements
join … in … on … equals … into …
Group Join … In … On …

Example of Join - Query Expression

using System;
using System.Collections.Generic;
using System.Linq;

namespace Operators
{
    class JoinTables
    {
        class DepartmentClass
        {
            public int DepartmentId { get; set; }
            public string Name { get; set; }
        }

        class EmployeeClass
        {
            public int EmployeeId { get; set; }
            public string EmployeeName { get; set; }
            public int DepartmentId { get; set; }
        }

        static void Main(string[] args)
        {
            List<DepartmentClass> departments = new List<DepartmentClass>();
            departments.Add(new DepartmentClass { DepartmentId = 1, Name = "Account" });
            departments.Add(new DepartmentClass { DepartmentId = 2, Name = "Sales" });
            departments.Add(new DepartmentClass { DepartmentId = 3, Name = "Marketing" });
            departments.Add(new DepartmentClass { DepartmentId = 4, Name = "Packing" });
            departments.Add(new DepartmentClass { DepartmentId = 5, Name = "Store" });
            departments.Add(new DepartmentClass { DepartmentId = 6, Name = "HR" });


            List<EmployeeClass> employees = new List<EmployeeClass>();
            employees.Add(new EmployeeClass { DepartmentId = 1, EmployeeId = 1, EmployeeName = "William" });
            employees.Add(new EmployeeClass { DepartmentId = 2, EmployeeId = 2, EmployeeName = "Miley" });
            employees.Add(new EmployeeClass { DepartmentId = 2, EmployeeId = 3, EmployeeName = "Benjamin" });
            employees.Add(new EmployeeClass { DepartmentId = 3, EmployeeId = 4, EmployeeName = "Mack" });
            employees.Add(new EmployeeClass { DepartmentId = 3, EmployeeId = 5, EmployeeName = "Sam" });
            employees.Add(new EmployeeClass { DepartmentId = 1, EmployeeId = 6, EmployeeName = "Rock" });
            employees.Add(new EmployeeClass { DepartmentId = 1, EmployeeId = 5, EmployeeName = "Sam" });
            employees.Add(new EmployeeClass { DepartmentId = 1, EmployeeId = 6, EmployeeName = "Rock" });


            var list = (from e in employees
                        join d in departments on e.DepartmentId equals d.DepartmentId
                        select new
                        {
                            EmployeeName = e.EmployeeName,
                            DepartmentName = d.Name
                        });

            foreach (var e in list)
            {
                Console.WriteLine("Employee Name = {0} , Department Name = {1}",
                                  e.EmployeeName, e.DepartmentName);
            }

            Console.WriteLine("\nPress any key to continue.");
            Console.ReadKey();
        }
    }
}

When the above code of C# or VB is compiled and executed, it produces the following result:

Author : Sandeep Kumar Jha

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