After reading this book, you should have a better understanding of OOP and the C# programming language. However, this isn't enough. You must push yourself to learn more about software development. You should learn the other language features of C# and how to use them to get your job done. You should also learn data structures and algorithms for your professional work. In the following list, I have suggested a number of topics and technologies to look into next:

• C# programming language features such as operators, control statements, arrays, lists, operator overloading, Lambda expressions, LINQ, string formatting, and threading
• Data structures and algorithms such as linked lists, binary trees, sorting, and searching algorithms.
• Web/desktop frameworks such as ASP.NET MVC, ASP.NET Web API, WPF, and WCF
• Frontend technologies such as HTML, CSS, and JavaScript, as well as Javascript frameworks such as reactjs/angular
• Database technologies such as MS SQL Server, Oracle, and MySQL
• Design patterns and their implications
• Software architecture and design
• Clean code, code refactoring, and code optimization

There are many other things to learn, but I have covered the topics I believe every software developer should know. This list is quite long and the topics are quite technical, so plan your learning carefully.