How to execute particular sql function in all databases of particular pC?

Question

How to execute particular sql function in all databases of  particular pC?
using frontend application using c#.

I have written one function in one datbase,
My Requiremment is i want to execute that function in all databases of server
using frontend app.
select database(dropdown)
execute function for that database(here execute is button)

How to do this?
any idea?
thanks inadvance