In this post I am adding a new template to our archive. This template is Windows Form Application templates which enables you to get user input for your API program. Sometimes in your Revit application you need to get user's input to achieve your goal. Designing windows from application is the most common approach to get the user input.
In order to add a windows form to your project, in Visual Studio right click on the your project in Solution Explorer. Then Add, Windows Form. Now you will have a class of Windows Form added to your project. You can right click on the Form1 and access to the background cod of the Form1 Design. You need to add some lines of code to your project which you can ind in the uploaded template.