、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

};

、内连接：

 var query = from t in entitiy.TB_GCGL_ADA_USER

                 join p in entitiy.TB_GCGL_ZY_ZYK

                 on t.ETPRS_CODE equals p.ETPRS_CODE

                 select new TB_USER_ZYK

                 {

                    USER_ID = t.USER_ID,

                    USER_NAME = t.USER_NAME,

                    USER_PASSWORD = t.USER_PASSWORD,

                 };