Can C# 8 Features Be Used in Older .NET Framework Applications?

C# 8 compatibility with .NET Framework

Question: Even though Visual Studio 2019 does not list C# 8 as an option for .NET Framework projects, is it compatible with legacy frameworks?

Answer: Yes, C# 8 is compatible with the .NET Framework and is compatible with target frameworks earlier than .NET Core 3.0/.NET Standard 2.1, even with earlier versions of NuGet packages installed Also compatible in Visual Studio 2019.

To incorporate C# 8 into these frameworks, simply adjust the language version to 8.0 in your csproj file or Directory.Build.props file to apply it to your entire solution. However, please note that some features may not be available depending on the target framework.

Supported functions:

• Static local function
• using statement
• Null merge assignment
• Read-only members
• Disposable ref structure
• Location Mode
• Tuple pattern
• switch expression
• Nullable reference type (with restrictions)

Features that require workarounds:

• Asynchronous streams: Use the "Microsoft.Bcl.AsyncInterfaces" NuGet package
• Indices and ranges: Use polyfill NuGet packages or code files

Unsupported features:

• Default interface members are not supported due to runtime limitations in the .NET CLR, as development of the .NET Framework has been superseded by .NET Core.

Implementation method:

To ensure compatibility, please edit your .csproj file to include the following:

<PropertyGroup>
  <LangVersion>8.0</LangVersion>
  <Nullable>enable</Nullable>
</PropertyGroup>

Starting with version 16.3, Visual Studio 2019 has disabled the language version drop-down menu for C# 8. However, it is still possible to set the language version by editing the project file.

Unofficial support:

While C# 8 supports the .NET Framework, Microsoft officially considers this combination unsupported and recommends expert-level understanding due to potential limitations and nuances.

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