1、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 };
2、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 };
3、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, };
