数据是通过OleDB加载到ado.net数据集中的本地CSV文件.该表有40列,包括发票明细.每行是发票中的单独的行项目,可以由1到n行组成.
该查询用于将发票详细信息分组为每个发票的单个行,总计发票金额和到期余额.
以下作品,我正在尝试确定：
是否可以在单个查询中执行此操作？
//group the invoices by invoicenumber and sum the total
//Zoho has a separate record (row) for each item in the invoice
//first select the columns we need into an anon array
var invoiceSum =
DSZoho.Tables["Invoices"].AsEnumerable()
.Select (x =>
new {
InvNumber = x["invoice number"],InvTotal = x["item price"],Contact = x["customer name"],InvDate = x["invoice date"],DueDate = x["due date"],Balance = x["balance"],} );
//then group and sum
var invoiceTotals =
invoiceSum
.GroupBy (s => new {s.InvNumber,s.Contact,s.InvDate,s.DueDate} )
.Select (g =>
new {
InvNumber = g.Key.InvNumber,InvDate = g.Key.InvDate,DueDate = g.Key.DueDate,Contact = g.Key.Contact,InvTotal = g.Sum (x => Math.Round(Convert.ToDecimal(x.InvTotal),2)),Balance = g.Sum (x => Math.Round(Convert.ToDecimal(x.Balance),} );
解决方法
实际上,当您使用invoiceTotals的结果时,您只会执行一个查询.在您正在显示的代码中,您甚至没有对数据库进行查询.
谷歌“linq延期执行”,这很漂亮;-)
但是如Uriil所说,您可以将语句组合成一个LINQ查询：
var invoiceSum =
DSZoho.Tables["Invoices"].AsEnumerable()
.Select (x =>
new {
InvNumber = x["invoice number"],}
)
.GroupBy (s => new {s.InvNumber,s.DueDate} )
.Select (g =>
new {
InvNumber = g.Key.InvNumber,}
);
