OpenSilver is a framework (successor of Silverlight) for building rich, browser-hosted applications that run on a variety of operating systems and devices, ranging from standard PCs to tablets and smartphones. It exposes a development ecosystem richer than the traditional blend of HTML, CSS and JavaScript, making you able to create applications with interactive graphics, vector animations, embedded videos, and so on, just designing the UI with XAML and programming the logic with code written in C# (or other .NET languages), in a way similar to programming in Microsoft WPF (Windows Presentation Foundation), but targeting the browser instead of the desktop. This book is an introductory guide to the OpenSilver world, targeted to developers with some experience on .NET development. Leveraging years of teaching experience, Alberto Venditti helps you and guide you along this journey in a simple and clear way, with practical and ready-to-use examples.