Linq中GroupBy和Where的语法

var query =
from rHead in mPlanDataTable.AsEnumerable()
where rHead.Field<String>("line") == sqlLine.Text
&& rHead.Field<String>("product_req_ym") == dtpYmd.Text.Replace("/", "")
&& rHead.Field<String>("supplier") == rHead.Field<String>("usercd")
&& rHead.Field<String>("supplier") == sqlLine.Text.Substring(sqlLine.Text.Length - 4, 4)
orderby rHead.Field<String>("itemno")
group rHead by new
{
line = rHead.Field<String>("line")
,
itemno = rHead.Field<String>("itemno")
,
supplier = rHead.Field<String>("supplier")
,
usercd = rHead.Field<String>("usercd")
,
product_req_ym = rHead.Field<String>("product_req_ym")
} into g
select new
{
line = g.Key.line,
itemno = g.Key.itemno,
type = g.Key.itemno.Substring(0, 4),
sy = g.Key.itemno.Substring(8, 6),

supplier = g.Key.supplier,
usercd = g.Key.usercd,
product_req_ym = g.Key.product_req_ym
};
foreach (var obj in query)
{
mTempDataTable.Rows.Add(obj.line
, obj.itemno
, obj.type
, obj.sy
, obj.supplier
, obj.usercd
, obj.product_req_ym);
}
}

Linq中GroupBy和Where的语法

原文：https://www.cnblogs.com/alwaysDoing/p/9360516.html