Question

感谢您的帮助。实际上我有一个数据表发票，包含invoice_no，Invoice_dt，material_name，unit_price等字段。

但我需要找到项目的unit_price，这是该材料的最后日期条目{max（invoice_dt）}是否可能？

var query = from t1 in invoice
        where t1.material_name == MyMaterial && t1.invoice_dt == (invoice.max(invoice_dt))
        select t1.unit_price;

从上面我的意图是获取unit_price的最新日期条目，这将是当前的市场价格......

Answer 1

var maxDate = invoice.Max(t1 => t1.invoice_dt);
var query = from t1 in invoice
        where t1.material_name == MyMaterial && t1.invoice_dt == maxDate)
        select t1.unit_price;

如果要检索最大日期项目的价格，并且发票按材料名称分组：

var groupedInvoices = invoice.GroupBy(t1 => t1.material_name);
foreach (var group in groupedInvoices)
{
    var maxDate = group.Max(t1 => t1.invoice_dt);
    var maxDateItem = group.Single(item => item.invoice_dt == maxDate);
    Console.WriteLine(maxDateItem.unit_price);
}

Answer 2

实现这一目标的最简单方法是我可以使用扩展方法：

var query = invoice.SingleOrDefault(item => item.invoice_dt ==
    invoice.Where(inv => inv.material_name == MyMaterial).
    Max(inv => inv.invoice_dt)).Select(i => i.unit_price);

从Datatable中查找值与其max（）值 - LINQ查询进行比较

2 个答案: