Creating Dynamic Datalist in Item Template in for loop

Hi ALL

I want to create dynamic datalist control with item template in a for loop.

Example: In my database, I have 20 Categories and 100 products. Each categories have some products. Now I want to show 20 categories all together in my page and it is not specific that categories will remain same. It can be increase or decrease. I am taking CategoryID with the help of for loop and now I want to bind datalist according to the count of for loop.

Kindly advice. How to achieve this?