var query1 = (from Employee employee1 in list1
join Department department1 in list
on employee1.Department equals department1.deptId into o
from department1 in o.DefaultIfEmpty()
select new Employee()
{
id=employee1.empId,
name=employee1.empName,
salary=employee1.empSalary,
departmentname=department1.deptName
});
You may have to adjust properties names according to how you defined the Employee class. I leave it as an exercise for you so that you can clearly understand how linq queries and results work.