//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 };