c# - 在 foreach 循环中抓取数据后如何返回预先排序的数据？

Question

首先，我正在获取 ClientID。然后，我得到与该 ClientID 关联的所有发票。我想返回所有按 InvoiceNumber 排序的数据，降序。这是我的代码：

var rvInvoices =
             (from i in db.QB_INVOICES_HEADER
                where i.ClientID == cId
                select i).ToList();
foreach (var itm in rvInvoices)
{
        InvoiceModel cm = new InvoiceModel()
        {
                InvoiceNumber = itm.InvoiceNumber,
                InvoiceSentDt = itm.InvoiceSentDt,
                InvoiceDt = itm.InvoiceDt,
                Amount = itm.Amount,
                Term = itm.Term,
                ClientName = itm.CI_CLIENTLIST.ClientName
        };

        listInvoices.Add(cm);
}

return listInvoices;

Answer 1

listInvoices.OrderByDescending(x => x.InvoiceNumber).ToList()

Answer 2

你应该尝试这样的事情：

var rvInvoices =
               (from i in db.QB_INVOICES_HEADER
                where i.ClientID == cId
                select i).OrderByDescending(x => x.InvoiceNumber);

而且我看不出你需要打电话的理由.ToList()。

Answer 3

您应该在数据库而不是客户端上订购它们：

var rvInvoices = db.QB_INVOICES_HEADER
    .Where(i => i.ClientID == cId)
    .OrderByDescending(i => i.InvoiceNumber);

Answer 4

您可以在三个地方下订单。

1. 在初始查询中，
2. 在foreach, 或
3. 在里面return

选项1：

var rvInvoices =
    (from i in db.QB_INVOICES_HEADER
    where i.ClientID == cId
    select i).OrderByDescending(i => i.InvoiceNumber).ToList();

选项 2：

foreach (var itm in rvInvoices.OrderByDescending(i => i.InvoiceNumber))

选项 3：

return listInvoices.OrderByDescending(i => i.InvoiceNumber).ToList();

我建议采用路线 1，因为它将在数据库级别运行订单。

Answer 5

您当前拥有的方法创建多个列表，具有显式foreach循环，并且需要对其输出进行排序。只需创建一个列表，无需显式循环，数据库为您进行排序即可完成：

return
    (from i in db.QB_INVOICES_HEADER
     where i.ClientID == cId
     // have the database do the sorting
     orderby i.InvoiceNumber descending
     select i)
     // break out of the DB query to make InvoiceModel
    .ToEnumerable()
    .Select(itm => new InvoiceModel()
    {
        InvoiceNumber = itm.InvoiceNumber,
        InvoiceSentDt = itm.InvoiceSentDt,
        InvoiceDt = itm.InvoiceDt,
        Amount = itm.Amount,
        Term = itm.Term,
        ClientName = itm.CI_CLIENTLIST.ClientName
    })
     // only create one list as the last step
    .ToList();