Null & Void - Everything about Nothing in .NET - Stefan Pölz - NDC London 2025

This talk was recorded at NDC London in London, England. #ndclondon #ndcconferences #developer #softwaredeveloper Attend the next NDC conference near you: https://ndcconferences.com https://ndclondon.com/ Subscribe to our YouTube channel and learn every day: / @NDC Follow our Social Media! https://www.facebook.com/ndcconferences https://twitter.com/NDC_Conferences https://www.instagram.com/ndc_conferences/ #dotnet #programminglanguages #csharp #api #roslyn #metadata System.NullReferenceException: 'Object reference not set to an instance of an object.' I used to read this message quite almost every day. But null references, also referred to as the "billion-dollar mistake" in that context, are also a great mechanism to express optionality and unavailability of a certain resource. There are great tools to help us deal with ... utilize null pointers. IDEs and Analyzers have introduced diagnostics which warn us at compile time about potential trouble at runtime. And recently the magnificent C# 8.0 has brought us nullable reference types: a language feature which lets us annotate our API to clearly communicate the design intent of nullability. So let's explore nullable reference types (including the accompanying nullable attributes of the BCL), their representation in both Reflection Metadata and the Roslyn API, and complement that with other available keywords and operators based on null. As a side effect, we will learn about the fundamental difference of nullable reference types and nullable value types in .NET. Additionally, we shall discover an alternative to null while still retaining the semantics of "nothing" - Spoiler: the null object pattern.