Hello every body, I want to build a simple plug in project. My concept is In my main form two textbox, 1 combo box & one button will be there. in combo box i want to load add, subtract, multy & division. After selecting any of then, button will be pressed and the method will done and show the result as message. But I want to build subtract,multiple & division as a plug in. If the plug in dll are found in bin/plugin folder then it load on combo box and after clicking button it works, other wise (if plug in dll not found) there will be one method add which i wrote in main window! Please Help Me. I am new in this area. Thank you In advance!