mapping column fields in code

in sql table i have fields which needs to be mapped with ALIAS field names

how to do the mapping when coding

currently i have

select *,,data_type  from mappingtable,information_schema.columns where   where mainfield='City' or aliasfield ='City'

execute query using reader

this table does not contain teh actual data

its contains onky the mainfield and its alias field name

i get City from a variable

i have  a second table which contains mainfield ie the column names & the actual data

then i use

if( reader["data_type"].ToString() == "numeric")

do something and so on

make label control visible true

else

make dropdown visible true

but there is lot of performnace and speed issue

wht wuld be the correct method so as to enhance the above