MS Access DB Query String Parameter Issue

Question

I'm having some trouble getting results from a c# OleDbCommand on an MS Access database. Here's my command:

SELECT START_DATE
FROM tblVisits
WHERE LocProj_IS_NUMBER = @projId
AND LocSTATN_IS_NUMBER = @statnId
AND LocSTATN_ORG_ID = @orgId
AND LocProj_ORG_ID = @orgId

If I call this using parameters, I get no results, BUT if I replace @orgId with 'GULN' then I get exactly what I expect. Programmatically, I'm getting the @orgId value from the SelectedValue property of a DropDownList. I'm baffled because this exact approach is working in a query to other tables in the same database.

Any ideas?

Answer 1

do you need to delimit your parameter values with quotes?

AND LocSTATN_ORG_ID = "'" + @orgId + "'"
AND LocProj_ORG_ID = "'" + @orgId + "'"

Answer 2

So here's what worked. I replaced all of the parameter names with question marks (thanks to this post) No idea why my previous queries were working without a hitch. I'm guessing that trying to reference the same parameter twice was the main problem.