Dynamic linq query with dynamic where conditions and from conditions - linq

Question

public GetApplicants(string Office,
int Id,
List<int> cfrparts,
List<int> expertiseAreaIds,
List<int> authIds,
List<int> specIds)
{
bool isAuthIdsNull = authIds == null;
authIds = authIds ?? new List<int>();
bool isSpecIdNull = specIds == null;
enter code here
var query =
from application in Apps
from cfr in application.cfr
from exp in cfr.Aoe
from auth in exp.Auth
from spec in exp.Special
where application.Design.Id == 14
where (iscfrpart || cfrPartIds.Contains(cfr.CfrP.Id))
where (isexp || expertiseAreaIds.Contains(exp.Aoe.Id))
where (isAuthIdsNull || authIds.Contains(auth.Auth.Id))
where (isSpecIdNull || specIds.Contains(spec.Special.Id))
where application.Office.Text.Contains(Office)
where application.D.Id == Id
select application.Id;
How can i make this query dynamic. If I have only Id and Office values It should still give me the resultset based on the avaliable values. Cureently its not giving me the result.

Answer 1

Instead of doing multiple calls to where, use &&
var query =
from Apps
where (iscfrpart || cfrPartIds.Contains(Apps.cfr.CfrP.Id))
&& (isexp || expertiseAreaIds.Contains(Apps.cfr.Aoe.Id))
&& (isAuthIdsNull || authIds.Contains(Apps.cfr.Aoe.Auth.Id))
&& (isSpecIdNull || specIds.Contains(Apps.cfr.Aoe.Special.Id))
&& Apps.Office.Text.Contains(Office)
&& Apps.D.Id == Id
select application.Id;
Additionally, this clause application.D.Id == 14 will cause 0 results when combined with this one: application.D.Id == Id if the passed in Id does not equal 14. You may want to delete that first clause.
Edit: updated your from clause, but I still don't think this will work because your table structure seems off.

Answer 2

Dynamic querying isn't required to solve this problem. You can write code that constructs the query.
Make a method that constructs your filter based on the information you have.
public Expression<Func<Application, bool>> GetFilterForCFR(List<int> cfrParts)
{
if (cfrParts == null || !cfrParts.Any())
{
return app => true;
}
else
{
return app => app.cfr.Any(cfr => cfrParts.Contains(cfr.cfrPId));
}
}
Then, you can construct the query using the expression.
var query = Apps;
var cfrFilter = GetFilterForCFR(cfrParts);
query = query.Where(cfrFilter);
//TODO apply the other filters
var finalquery = query.Select(app => app.Id);