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The following are the different types of joins in LINQ
Group Join – Discussed in Part 21
Inner Join
Left Outer Join
Cross Join
In this video we will discuss implementing INNER JOIN in LINQ. If you have 2 collections, and when you perform an inner join, then only the matching elements between the 2 collections are included in the result set. Non – Matching elements are excluded from the result set.
Let us understand Inner Join with an example.
Example 1 : Join the Employees and Department collections and print all the Employees and their respective department names.
var employees = Employee.GetAllEmployees().Join(Department.GetAllDepartments(), e =] e.DepartmentID,
d =] d.ID, (employee, department) =] new
{
EmployeeName = employee.Name,
DepartmentName = department.Name
});
foreach (var employee in employees)
{
Console.WriteLine(employee.EmployeeName + “t” + employee.DepartmentName);
}
Output: Notice that, in the output we don’t have Andy record. This is because, Andy does not have a matching department in Department collection. So this is effectively an inner join.
Example 2 : Rewrite Example 1 using SQL like syntax.
var employees = from e in Employee.GetAllEmployees()
join d in Department.GetAllDepartments()
on e.DepartmentID equals d.ID
select new { EmployeeName = e.Name, DepartmentName = d.Name };
foreach (var employee in employees)
{
Console.WriteLine(employee.EmployeeName + “t” + employee.DepartmentName);
}
