Nullable object must have a value
阿新 • • 發佈:2019-04-25
ble fault 就會 nullable 一個 where empty 有一個 inner
有一個linq查詢,由inner join改成left join, 對於有空值,就會出現Nullable object must have a value 的錯誤.
原來的查詢:
var qry = from c in _context.CCC join f in _context.FFF .Where(t=>t.IsActive==true) on new { c.ProjectId, cat = c.Category } equals new { f.ProjectId, cat = f.Category }where c.IsActive == true select new { c.Id, f.category }
left join, select的字段做null判斷
var qry = from c in _context.CCC join f in _context.FFF .Where(t=>t.IsActive==true) onnew { c.ProjectId, cat = c.Category } equals new { f.ProjectId, cat = f.Category } into temp from tt in temp.DefaultIfEmpty() where c.IsActive == true select new { c.Id, category=(f==null)?‘‘:f.category }
Nullable object must have a value