get particular record from 1 datalist to 2nd datalist

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ASP.NET

i have created 2 datalist 1'st is catalogue & 2'nd is cat_detail

now my que is in catalogue i select pizza in 2'nd datalist which is cat_detail i want only pizza records

in detail
catalogue tbl=cat_id,cat_nm for ex:1,pizza
2,pasta
cat_detail tbl=id,cat_id,name,type,price,des.
for ex:1,1,margherita pizza,veg,200,abc.
2,1,mashroom riot,veg,200,xyz
3,2,italian pasta,veg,150,pqr