I have created this query to fetch some result from database. Here is my table structure.
What exaclty is happening.
DtMapGuestDepartment as Table 1
DtDepartment as Table 2
Are being used
var dept_list= from map in DtMapGuestDepartment.AsEnumerable()
where map.Field<Nullable<long>>("GUEST_ID") == DRowGuestPI.Field<Nullable<long>>("PK_GUEST_ID")
join
dept in DtDepartment.AsEnumerable()
on map.Field<Nullable<long>>("DEPARTMENT_ID") equals dept.Field<Nullable<long>>("DEPARTMENT_ID")
select dept.Field<string>("DEPARTMENT_ID");
I am performing this query on DataTables and expect it to return me a datatable.
Here I want to select distinct department from Table 1 as well which will be my next quest. Please answer to that also if possible.
break your query into parts and see which collection has no elements.
var mapList = DtMapGuestDepartment.AsEnumerable().ToList();
var deptList = DtDepartment.AsEnumerable().ToList();
var queryResult1 = (
from map in mapList
where map.Field<Nullable<long>>("GUEST_ID") ==
DRowGuestPI.Field<Nullable<long>>("PK_GUEST_ID")
select map
).ToList();
var queryResult2 = (
from map in queryResult1
join dept in deptList
on map.Field<Nullable<long>>("DEPARTMENT_ID")
equals dept.Field<Nullable<long>>("DEPARTMENT_ID")
select dept.Field<string>("DEPARTMENT_ID")
).ToList();