You can use the below linq query for first scenario,
- Assign -> dt_Output = dt_Input.asenumearble().where(Function(X) X("Do no.").toString.equals("10923")).Copytodatatable()
use the below linq for second scenario,
- Assign -> LIst_Country = (From row in dt_Input
where row("Do no.").equals("10923")
Select row("Country")
).Tolist()
Hope it helps!!