How to populate gridview and dropdown menu based on another dropdown

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ASP.NET

Hello, hope someone can help.

I have a form with two dropdown lists (campus, and rooms) and a gridview to show available assets. I would like to populate the 'room' dropdown list and update the gridview based on the campus the user choose, i.e. if a user choose London campus, I want the rooms in that campus to populate the second dropdown, and available asset to populate the gridview.

I have tried to use the databind wizard in asp.net, but nothing actually show when running the application, not even the gridview. I am not that good with the code behind, although I tried it few time.

autopostback is true for campus dropdown list.
room dropdown will show the rooms only if campusCampus = campusRoom
gridview will display assets only if campusCampus = assetsCampus

hope you are able to help

thanks in advance