A First Look at .NET Core 3.0

.NET Core has already established itself as a powerful, cross-platform framework for building web applications and services. But with the upcoming release of .NET Core 3.0, the platform is set to take its biggest leap forward yet. The preview releases have shown a host of major new features that will significantly expand the capabilities of .NET Core and change how developers write C# code.

This is shaping up to be one of the most important releases in the history of .NET.

1. Desktop Application Support: WPF and Windows Forms

This is the headline feature. For the first time, .NET Core will support the creation of Windows desktop applications using Windows Presentation Foundation (WPF) and Windows Forms. This is a game-changer for developers who want to modernize their existing desktop applications or build new ones that can take advantage of the performance improvements and deployment flexibility of .NET Core.

While the UI frameworks themselves will remain Windows-only, the rest of the application can be built on the cross-platform .NET Core base.

2. C# 8.0 and Nullable Reference Types

.NET Core 3.0 will ship with C# 8.0, which introduces one of the most significant new language features ever: nullable reference types. This feature aims to solve the "billion-dollar mistake"—null reference exceptions.

By enabling this feature, the compiler will treat all reference types (like string) as non-nullable by default. If you want a variable to be able to hold null, you must explicitly declare it with a ? (e.g., string?). The compiler will then perform a static analysis of your code and warn you if you try to dereference a potentially null variable without checking it first.

#nullable enable

string name = null; // Compiler warning: Cannot convert null to non-nullable type

string? middleName = null; // This is allowed

Console.WriteLine(middleName.Length); // Compiler warning: Dereference of a possibly null reference

This feature will fundamentally change how C# developers write code, leading to more robust and reliable applications.

3. High-Performance JSON APIs

.NET Core 3.0 includes a brand new, high-performance, low-allocation JSON serializer: System.Text.Json. This new library is built from the ground up to be fast and efficient, leveraging modern C# features like Span<T>. It's set to become the new standard for JSON manipulation in .NET, reducing the dependency on the popular third-party Newtonsoft.Json library.

4. First-Class Support for gRPC

Microsoft is making a big bet on gRPC as a modern, high-performance alternative to REST for service-to-service communication. .NET Core 3.0 will have first-class, built-in support for creating and hosting gRPC services, making it easier than ever to build high-performance microservices.

5. Single-File Executables

.NET Core 3.0 will introduce the ability to publish an application as a single executable file. This will bundle the application and all its dependencies (including the .NET Core runtime if desired) into a single file, dramatically simplifying deployment.

Conclusion

.NET Core 3.0 is poised to be a massive release. The addition of desktop support brings a huge ecosystem of existing applications into the modern .NET world, while C# 8.0's nullable reference types will forever change how we write C# code for the better. With its focus on performance, modern communication protocols like gRPC, and improved deployment options, .NET Core 3.0 is solidifying its position as a top-tier framework for building any type of application.