[英]Using result of let in where clause LinQ
我正在使用Linq To SQL从数据表中获取数据。 我想在where子句中使用let语句的结果。
例如:-
from t1 in table1
join t2 in table2
on t1.field1 equals t2.field2
let calculatedValue = t2.val1 + t2.val2
join t3 in table3
on t2.somefield equals t3.somefield
into t3Grp
from subt3 in t3Grp.DefaultIfEmpty()
[select the row in table3 with where table3.someValue < calculatedValue]
在.Where()
子句中无法访问calculatedValue中遇到的问题。 我想要全左联接输出(即,即使在table3中没有某行具有someValue < calculatedValue
我也希望在输出中该行。请帮忙。
尝试这个:
from t1 in table1
join t2 in table2
on t1.field1 equals t2.field2
let calculatedValue = t2.val1 + t2.val2
join t3 in table3.where(item => item.someValue < calculatedValue)
on t2.somefield equals t3.somefield
into t3Grp
from subt3 in t3Grp.DefaultIfEmpty()
select new
{
val1= table3.val1,
val2 = table3.val2,
.
.
.
}
您可以通过在最终select
限制t3Grp
来做到这一点t3Grp
,例如
from t1 in table1
join t2 in table2
on t1.field1 equals t2.field2
let calculatedValue = t2.val1 + t2.val2
join t3 in table3
on t2.somefield equals t3.somefield
into t3Grp
from subt3 in t3Grp.DefaultIfEmpty()
select new { t1, t2, t3Grp = t3Grp.Where(t3 => t3.someValue < calculatedValue) }
该值在范围内 ,我不确定您想要的确切投影。
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