创建新的 Linq SelectMany 扩展方法
我正在使用 Linq.Dynamic。我已经向 all 添加了另一个 SelectMany 扩展，用于使用数据创建新的匿名对象。但是，我遇到了另一个我似乎无法解决的问题。
我想要按如下方式链接扩展方法，但使用动态方法：
var customerandorderflat = db.Customers
.SelectMany(c => c.Orders.SelectMany(o => o.Order_Details,
(ord, orddetail) => new
{
OrderID = ord.OrderID,
UnitPrice = orddetail.UnitPrice
}).DefaultIfEmpty(),
(cus, ord) => new
{
CustomerId = cus.CustomerID,
CompanyName = cus.CompanyName,
OrderId = ord.OrderID == null ? -1 : ord.OrderID,
UnitPrice = ord.UnitPrice
});
理想情况下，我想按如下方式链接动态 SelectMany：
db.Customers.SelectMany(c => c.Orders.SelectMany("Order_Details", "new(outer.OrderID, inner.UnitPrice)"), "new(outer.CustomerID, inner.OrderID)");
或有影响的东西。问题是我无法获得匹配的签名。
我尝试了许多不同的选项来让它允许链接。但它就是行不通。我认为理想情况下它看起来像这样：
public static IQueryable SelectMany(this IQueryable source, IQueryable innerExpression, string resultsSelector, params object[] values)
但是，它不识别 c => c. 订单为 IQueriable。我还需要弄清楚如何对结果执行 DefaultIfEmpty 以允许 LEFT JOIN。
请帮忙。
I am using Linq.Dynamic. I have already added another SelectMany extension to all for creating a new anonymous object with the data. But, I have ran into another issue that I can not seem to solve.
I want to have extension method chaining as follows, but using the dynamic methods:
var customerandorderflat = db.Customers
.SelectMany(c => c.Orders.SelectMany(o => o.Order_Details,
(ord, orddetail) => new
{
OrderID = ord.OrderID,
UnitPrice = orddetail.UnitPrice
}).DefaultIfEmpty(),
(cus, ord) => new
{
CustomerId = cus.CustomerID,
CompanyName = cus.CompanyName,
OrderId = ord.OrderID == null ? -1 : ord.OrderID,
UnitPrice = ord.UnitPrice
});
Ideally I would like to chain the dynamic SelectMany as follows:
db.Customers.SelectMany(c => c.Orders.SelectMany("Order_Details", "new(outer.OrderID, inner.UnitPrice)"), "new(outer.CustomerID, inner.OrderID)");
Or something to that affect. The problem is that I can not get a signature to match.
I have tried many different options to get it to allow chaining. But it just doesn't work. I am thinking ideally it would look like this:
public static IQueryable SelectMany(this IQueryable source, IQueryable innerExpression, string resultsSelector, params object[] values)
But, it doesn't recognize c => c.Orders as IQueriable. I also need to figure out how to do DefaultIfEmpty on the results to allow for LEFT JOINs.
Please help.
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c.Orders是一个 EntitySet。 EntitySet 不实现 IQueryable。尝试c.Orders.AsQueryable()c.Ordersis an EntitySet. EntitySet doesn't implement IQueryable. Tryc.Orders.AsQueryable()它得到了错误的定义。正确定义时的实际错误：无法将 lambda 表达式转换为类型“System.Linq.IQueryable”，因为它不是委托类型
It was getting the wrong definition. Actual error when on right definition: Cannot convert lambda expression to type 'System.Linq.IQueryable' because it is not a delegate type