The purpose is to learn and apply the fundamentals of C# OOP language. It's a windows desktop application for libraries, where they can store customer personal data and their borrowed books.

1. Open the solution and run the app.
2. In the first GUI, you can add, delete, edit new lenders and sort them from id, last name or borrow date.  
3. When you add or edit a lender, a second GUI opens, there inserts its personal information. 
4. In the second GUI press the button "Book Manager" to open the third GUI. Here you add the ISBN, author, title, genre of the book and the borrow date. You can edit or delete the lender booklist.

1.  Create a local SQL database for data storage and a class for connecting to it.