在Linq to Entity 中使用lambda表達式來實現Left Join和Join

1、讀取用戶和部門兩個表的左連接：

var sg = db.Users.GroupJoin(db.Departments, u => u.DepartmentId, d => d.DepartmentId, (u,d) => new { u, d }).Select(o=>o).ToList();

注意：上面將返回所用用戶信息和對應的部門信息（即用戶部門ID信息缺少，那么用戶列表也會顯示）

 

2、讀取指定返回列表字段的左連接信息：

 var GJoinList = db.Sys_User.GroupJoin(db.Sys_Department, u => u.DepartmentId, d => d.DepartmentId, (u,d) => new { UserId=u.UserId, Account=u.Account, RealName=u.RealName, EnabledMark=u.EnabledMark, DeleteMark=u.DeleteMark,DepartmentName = d.FirstOrDefault(x=>x.DepartmentId==u.DepartmentId).FullName}).Select(o=>o);

 

3、讀取連接表：

var sg = db.Users.Join(db.Departments, u => u.DepartmentId, d => d.DepartmentId, (u,d) => new { u, d }).Select(o=>o).ToList();

注意：這里將只顯示用戶里DepartmentId和部門表里DepartmentId相等的信息，如果用戶沒有部門ID則此條用戶信息不會顯示

 

 var data = db.CRM_OrderDetails.Join(db.CRM_Order, d => d.OrderId, o => o.OrderId, (d, o) => new { d, o }).Select(p => new ProductsListModel() {
                OrderId =p.o.OrderId,
                OrderCode=p.o.OrderCode,
                CustomerName=p.o.CustomerName,
                ProductName=p.d.ProductName,
                UnitId=p.d.UnitId,
                Qty=p.d.Qty,
                Price=p.d.Price,
                Amount=p.d.Amount,
                TaxAmount=p.d.TaxAmount,
                TaxCostAmount=p.d.TaxCostAmount,
                CreateTime=p.d.CreateTime,
                EndTime=p.d.EndTime,
                Description=p.d.Description
            }).Where(expression).OrderBy(orderbyExpression);