accessing class file outside App_Code folder

Hi, I have a single project. and I have two folder in it. In the 1st folder I have a class named Class1 and in the 2nd folder I have a class named Class2. Can anyone tell me how I can access members of Class1 in Class2. I have tried by adding namespace in Class1 and Using that namespace in Class2. But it is giving error. It is easy to access classes or their members from App_Code folder. I don't want to put my classes in app_code folder. Thanks in Advance
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