C# Singleton Pattern Explained with Code Examples for Console and ASP.NET Core

A tutorial published on DEV Community introduces the Singleton design pattern in C#, explaining how it restricts a class to a single instance accessible throughout an application. The pattern is commonly used to manage shared resources such as configuration, logging, and caching without the overhead of multiple instances. Two key implementation rules are highlighted: using a sealed class modifier to prevent subclassing and a private constructor to block external instantiation. The article demonstrates practical usage through code samples built in Microsoft Visual Studio 2026, including a console app and an ASP.NET Core Razor Pages project. A month-list dropdown feature serves as the working example, showing how Lazy<T> handles thread safety and lazy initialization automatically.