New in .NET 10.0 [3]: C# 14.0

In a .NET 10.0 project (project setting in .csproj file: <TargetFramework>net10.0</TargetFramework>), C# language version 14.0 is the automatically set default, even without an additional tag <LangVersion>.

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C# 14.0 is officially supported by Microsoft only from .NET 10.0 onwards. Microsoft's Learn site states: “C# 14.0 is supported only on .NET 10 and newer versions.”

However, developers can use some (but not all!) C# 14.0 language features in older .NET versions, including .NET Framework, .NET Core, and Xamarin, at their own risk. To achieve this, you need to increase the <LangVersion> in the project file (.csproj) to “14.0”:

<PropertyGroup>
  <TargetFramework>.net8.0</TargetFramework>
  <LangVersion>14.0</LangVersion>
</PropertyGroup>

Please note, however, that there is no technical support from Microsoft for the use of C# 14.0 language features in .NET versions before 10.0. In case of problems, you cannot use your support contract to ask Microsoft for help. Nevertheless, using higher C# versions in older .NET projects is common and trouble-free practice in some companies.

Compared to version 13.0, eight significant new features have appeared in C# 14.0 (which will be presented in this blog series in the coming weeks):

• New operator overloads for +=, -=, *=, /=, %=, &=, |=, ^=, <<=, >>=, and >>>
• Extension blocks with the keyword extension
• Semi-auto properties with the keyword field (these already existed in C# 13.0, but experimentally)
• Partial constructors and partial events
• Null-conditional assignment
• Simplification for nameof() with generic types
• Simplifications for lambda expressions
• More conversions for spans

Of the new language features in .NET 10.0 mentioned above, all but one work in older .NET versions as well, provided you set <LangVersion>latest</LangVersion> in the project file. The exception is the new operator overloads. These will be covered in the next article in this series.

(mki)