我正在尝试编写一条语句以获取实体框架中两个字段的乘积之和。
给出以下结构:
public class Order
{
public int OrderNUmber {get; set;}
public virtual List<Orderline> OrderLines {get; set;}
public virtual List<ServiceLine> ServiceLines {get; set;}
public string someproperty {get; set;}
}
public class OrderLine
{
public string productname {get; set;}
public int quantity {get; set;}
public decimal price {get; set;}
}
public class ServiceLine
{
public string servicename {get; set;}
public int quantity {get; set;}
public decimal rate {get; set;}
}
我正在尝试通过一个查询返回总订单价值:
var GrandTotal = Orders.Where(q => q.someproperty == "somecondition")
.Sum(order =>
order.OrderLines.Sum(line => line.quantity * line.price)
+ order.ServiceLines.Sum(sl =>sl.quantity * sl.rate));
但是此版本的确会得到正确的总数。该数字比预期的少。
所以这里的问题是,对于没有任何服务线的任何订单,EF都得到一个空值,而不是添加零。
这两个选项均起作用:
.Sum(
order =>
order.OrderLines.Select(n => new{n.quantity, n.price}).DefaultIfEmpty(new {quantity = 0, price = decimal.Zero}).Sum(line => line.quantity * line.price) + order.ServiceLines.Select(n => new{n.quantity, n.rate}).DefaultIfEmpty(new {quantity = 0, rate = decimal.Zero}).Sum(acl =>acl.quantity * acl.rate)
);
和
.Sum(
order =>
order.OrderLines.Select(lines => new { LineTotal = lines.quantity * lines.price }).DefaultIfEmpty(new { LineTotal = Decimal.Zero }).Sum(x => x.LineTotal) + order.ServiceLines.Select(acl => new { AclTotal = acl.quantity * acl.rate }).DefaultIfEmpty(new { AclTotal = Decimal.Zero }).Sum(x => x.AclTotal)
);
必须告诉EF匿名对象的DefaultIfEmpty值,否则它将用null破坏加法。因此,EF将获得OrderLineTotal(值)+ ServiceLineTotal(NULL)= NULL。