使用where子句LinQ的结果

Question

I am using Linq To SQL to get data from from data tables. I want to use the result of a let statement in a where clause.

eg:-

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]

The proble I face in calculatedValue is not accessible in .Where() clause of table3. I want fully left join output( ie; even if there is no row in table3 having someValue < calculatedValue i want that row in the output. Please help.

Answer 1

Try This:

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,
    .
    .
    .
  }

Answer 2

Can you do this by restricting t3Grp in your final select , eg

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) }

The value is in scope there, I'm just not sure of the exact projection you want.