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Microsoft Quietly Updates .NET Language Strategy

On February 6th 2023, Kathleen Dollard, principal program manager on .NET team at Microsoft, posted an update of the .NET language strategy. The new document is a continuation of the same ideas from the previous one, written in 2017, where C# and F# are the evolving languages, and VB.NET is a niche language.

The new strategy document is hosted on the Microsoft Learn site. It is broken down into three major .NET languages: C#, F# and VB.NET.

C# is recognised as the language with the broadest usage in the .NET community. Therefore, it will be evolved aggressively to remain a "state-of-the-art programming language". The team states clearly that they favour the design decisions that benefit the most developers, shying away from specialised enhancements for C#. At the same time, maintaining "a high commitment to backward compatibility" will mean that the team will consider the scale and the impact of any breaking change on the whole C# ecosystem.

One of the prominent comments from C# developers on the language evolution is the continuing existence of many legacy structures, such as non-generic collections (like ArrayList from the first version of .NET) or native event support (largely obsolete in the async world of modern C#). Immo Landwerth, a program manager on the .NET framework team at Microsoft, recognises that the team already tried launching a new .NET without the legacy components in Windows 8 era and that "it has proven to be completely unworkable" and "breaking the entire ecosystem". It is then probable to assume that those features will be kept in C# for a long time.

F# language strategy will be focused on providing "language leadership and guidance" in the first place. The language benefits from the community contributions significantly more than C#. To help keep the contribution quality high, Microsoft will support the technical decision-making and provide architectural direction.

There are two remaining strategy highlights for F#. One is to keep it interoperable with the new C#, recognising that C# and F# are often used together in real-world solutions. The other is simplifying the entry barrier for new F# developers, which may include rephrasing error messages and redesigning the language features for simplicity.

Visual Basic.NET (VB.NET) will be maintained to keep up with the new runtime and libraries’ enhancements without any new features specifically added to the language. The side-to-side co-evolution of the .NET languages was abandoned already in the first .NET strategy document in 2017, leaving VB.NET with something called a "consumption-only approach". According to the annotated strategy document, it means that VB.NET will be able to access the new .NET runtime and API enhancements via the normal .NET cross-language interop mechanism of the common language runtime (CLR), but it won’t have any new syntax to define the new features in VB.NET code.

Replying to a developer comment on the strategy announcement blog post page, Kathleen Dollard answered that "consumption-only" means that VB.NET developers won’t be able to create Span and Memory structs but that they will be able to call methods in C# that return them.

It is also clear from the stated focus on "stable design" and "core VB scenarios" that Microsoft won’t extend either the design of VB.NET language or its workloads, largely grouped around Windows Forms applications or libraries. Furthermore, there is an explicit sentence where Microsoft "does not anticipate" supporting web front ends (meaning Blazor) or cross-platform UI frameworks (meaning MAUI).

Older .NET languages such as C++/CLI have been omitted from the strategy, although it’s stated in the comments of the announcement that those languages aren’t managed by the .NET language product team. The developers comment on social media that they are confused about what actually are the changes in the strategy.

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