如何使用 LINQ to SQL 中的 Sum， GroupBy 计算总计

你能帮忙把它翻译成linq c#吗，我试过但没有成功。

SELECT od.ProductID, p.productName, SUM (od.UnitPrice * od.Quantity) as total 
FROM products p 
JOIN [order Details] od ON od.ProductId = p.ProductId
GROUP BY od.ProductId, p.productName
ORDER BY productID ASC

我已经尝试过这个，但它给了我一个错误：

var query =
    (from od in dal.Order_Details
        join p in dal.Products on od.ProductID equals p.ProductID
        group p by new {od.ProductID, p.ProductName}
        into g
        select new pintar
        {
            //  orderId = g.Key.OrderID,
            productId = g.Key.ProductID,
            productName = g.Key.ProductName,
            UnitPrice = od.UnitPrice,
            Quantity = od.Quantity,
            Discount = od.Discount,
            total = sum((g.Key.UnitPrice * g.Key.Quantity))
        }
        ).ToList();

var query =
    (from od in dal.Order_Details
        join p in dal.Products on od.ProductID equals p.ProductID
        group od by new {od.ProductID, p.ProductName}
        into g
        select new pintar
        {
            productId = g.Key.ProductID,
            productName = g.Key.ProductName,
            total = g.Sum(a => a.UnitPrice * a.Quantity))
        }
        ).ToList();