Using union inside a foreach loop for linq to sql - linq

Question

In the below code I expect to retrn n rows but it always returns zero rows as my initial set has zero records. Ideally it should be doing a UNION ALL and returning me records for all of the integers in the integer list clearanceTotals{6,7,8,9,17}
Any idea how to go about it?
var tbl = (from a in db.Applicants
where a.Id == null
select new { a.Id, a.Firstname, a.Lastname });
int thisTag;
foreach (int c in clearanceTotals)
{
switch (c)
{
case 6:
thisTag = 38;
break;
case 8:
thisTag = 39;
break;
case 17:
thisTag = 39;
break;
case 7:
thisTag = 42;
break;
case 9:
thisTag = 44;
break;
}
tbl = (from a in db.Applicants
join ad in db.ApplicantDeployments on a.Id equals ad.ApplicantId
join aa in db.ApplicantAttachments on a.Id equals aa.ApplicantId
where a.Nationality == 15 && a.DoNotUse == false && a.ClearanceStatus == c
&& aa.Tag == thisTag
select new { a.Id, a.Firstname, a.Lastname }).Union(tbl);
}

Answer 1

I think the problem is that you're capturing the loop variable (c) in the query, so when the query is executed, it uses only the latest value of c. Try copying c to a variable inside the loop:
foreach (int c in clearanceTotals)
{
int c2 = c;
...
...
where a.Nationality == 15 && a.DoNotUse == false && a.ClearanceStatus == c2
...

Answer 2

OK so i got this to work but its additional code plus additional variables
var temp = (from a in db.Applicants
where a.Id == null
select a.Id).ToList();
int thisTag;
foreach (int c in clearanceTotals)
{
switch (c)
{
case 6:
thisTag = 38;
break;
case 8:
thisTag = 39;
break;
case 17:
thisTag = 39;
break;
case 7:
thisTag = 42;
break;
case 9:
thisTag = 44;
break;
}
temp = temp.Union(from a in db.Applicants
join ad in db.ApplicantDeployments on a.Id equals ad.ApplicantId
join aa in db.ApplicantAttachments on a.Id equals aa.ApplicantId
where a.Nationality == 15 && a.DoNotUse == false && a.ClearanceStatus == c
&& aa.Tag == thisTag
select a.Id).ToList();
}
var tbl = (from a in db.Applicants
join ad in db.ApplicantDeployments on a.Id equals ad.ApplicantId
where temp.Contains(a.Id)
select new { a.Id, a.Firstname, a.Lastname }).Distinct();