How to enable Nullable Reference Types feature of C# 8.0 for the whole project

Question

According to the C# 8 announcement video the \"nullable reference types\" feature can be enabled for the whole project.

But how to enable it for the project? I did n

Answer 1

Legacy csproj format

You asked about the legacy .csproj format. Open up the project file in a text editor and make the following changes:

1. Add/change 8.0 in the Debug and Release PropertyGroup sections:

    
       preview
   

2. Enable support for nullable reference types by adding enable to the main PropertyGroup:

    
       enable
   

Tested with a .NET WinForms app using C# 8 and nullable reference types syntax in Visual Studio 2019 v16.2.0 Preview 3.

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SDK-style project files

SDK style projects are much simpler, and can be edited within Visual Studio. For these all you need is (in the same PropertyGroup as TargetFramework or TargetFrameworks):

  
    8.0
    enable
  

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Notes

• .NET Core 3.x projects target C# 8 by default, so you won't need to specify the LangVersion for those projects.

• The default for .NET Framework projects is C# 7.3, and you don't get C# 8.0 even with latest. You must explicitly set the language version to 8.0. Please refer to my answer to the question Does C# 8 support the .NET Framework? for more details.