Linq 实现左连接，右连接

左连接：

var LeftJoin = from emp in ListOfEmployees

join dept in ListOfDepartment on emp.DeptID equals dept.ID into JoinedEmpDept

from dept in JoinedEmpDept.DefaultIfEmpty()

select new

{

　　　　　　　　　　EmployeeName = emp.Name,

　　　　　　　　　　DepartmentName = dept != null ? dept.Name : null

};

右连接：

var RightJoin = from dept in ListOfDepartment

join employee in ListOfEmployees on dept.ID equals employee.DeptID into joinDeptEmp

from employee in joinDeptEmp.DefaultIfEmpty()

select new

{

　　　　　　　　　　EmployeeName = employee != null ? employee.Name : null,

　　　　　　　　DepartmentName = dept.Name

　　　　};