Linq to Entities Join、Group、Sum with Northwind Orders

Question

我正在尝试编写一个 linq 查询，它应该对 Northwind.mdb 中的 order_detail 行求和，然后 return 汇总总数以及负责员工的一些详细信息。我正在使用 LINQpad 对其进行测试，这是我目前所拥有的

void Main()
{
    var result = (from e in Employees
        join o in Orders on e.EmployeeID equals o.EmployeeID
        join d in OrderDetails on o.OrderID equals d.OrderID
        where o.OrderID == 10250
        group new { e, o, d } by new 
        {
             o.OrderID, e.Address, e.BirthDate, e.City, e.Country,
             e.LastName, e.FirstName, e.Title, e.TitleOfCourtesy, e.HireDate,
             e.Region, e.PostalCode, e.HomePhone,
             e.Extension, e.ReportsTo,e.PhotoPath, e.EmployeeID,
             d.Quantity, d.UnitPrice, d.Discount
        }
        into grp select new   
        {
            Name = grp.Key.FirstName + " " + grp.Key.LastName,
            OrderID = grp.Key.OrderID,      
            Address = grp.Key.Address,
            SalesTotal = grp.Sum(x => x.d.UnitPrice * x.d.Quantity)
        });

        result.Dump();       
}

Output from LINQPad

我只期待一行，总计 1813.00。有人可以告诉我我做错了什么吗？

Answer 1

您没有在正确的级别分组。如果将其更改为按员工分组，那么您应该会得到正确的结果：

void Main()
{
    var result = (from e in Employees
        join o in Orders on e.EmployeeID equals o.EmployeeID
        join d in OrderDetails on o.OrderID equals d.OrderID
        where o.OrderID == 10250
        group new { e, o, d } by new 
        {
             e.EmployeeID, e.FirstName, e.LastName, e.Address
        }
        into grp select new   
        {
            Name = grp.Key.FirstName + " " + grp.Key.LastName,
            Address = grp.Key.Address,
            SalesTotal = grp.Sum(x => x.d.UnitPrice * x.d.Quantity)
        });

        result.Dump();       
}

如果您希望每个订单一行，也按此分组：

void Main()
{
    var result = (from e in Employees
        join o in Orders on e.EmployeeID equals o.EmployeeID
        join d in OrderDetails on o.OrderID equals d.OrderID
        where o.OrderID == 10250
        group new { e, o, d } by new 
        {
             e.EmployeeID, e.FirstName, e.LastName, e.Address,
             o.OrderID
        }
        into grp select new   
        {
            Name = grp.Key.FirstName + " " + grp.Key.LastName,
            OrderID = grp.Key.OrderID,
            Address = grp.Key.Address,
            SalesTotal = grp.Sum(x => x.d.UnitPrice * x.d.Quantity)
        });

        result.Dump();       
}

Linq to Entities Join、Group、Sum with Northwind Orders

Linq to Entities Join, Group, Sum with Northwind Orders

c#

linq

linqpad