Visual Studio :: Cannot Access File From One Project To Another

i'm trying an example by trying to creating two projects in one solution to seperate logic and UI. so let's say test.logic and test.ui

in test.ui i have a page called lets say contact me. in the code behind for this page i want to call a method that belongs in a class called processData in test.logic

in contact me cs i tried something like:

namespace test.ui
{
using test.logic
//code here
}

but that does not work as class/method not shown in intellisense.