Hafner.Compatibility.NullableReferenceTypeAttributes (nuget): Defines the nullable reference type attributes of namespace System.Diagnostics.CodeAnalysis for frameworks that do not include them, namely .NET Framework 2.0 to 4.8, .NET Core 1.0 to 2.2 and .NET Standard 1.0 to 2.2.        Usage:        <Project Sdk="Microsoft.NET.Sdk">          <PropertyGroup>           <TargetFrameworks>net6.0;net5.0;netcoreapp3.1;netcoreapp3.0;netcoreapp2.2;netcoreapp2.1;netcoreapp2.0;netcoreapp1.1;netcoreapp1.0;netstandard2.1;netstandard2.0;netstandard1.6;netstandard1.5;netstandard1.4;netstandard1.3;netstandard1.2;netstandard1.1;netstandard1.0;net48;net472;net471;net47;net462;net461;net46;net452;net451;net45;net403;net40;net35;net30;net20</TargetFrameworks>           <FrameworksLackingNullableReferenceTypeAttributes>|net20|net30|net35|net40|net403|net45|net451|net452|net46|net461|net462|net47|net471|net472|net48|netcoreapp1.0|netcoreapp1.1|netcoreapp2.0|netcoreapp2.1|netcoreapp2.2|netstandard1.0|netstandard1.1|netstandard1.2|netstandard1.3|netstandard1.4|netstandard1.5|netstandard1.6|netstandard2.0|</FrameworksLackingNullableReferenceTypeAttributes>           <LangVersion>latest</LangVersion>           <Nullable>enable</Nullable>           <NoWarn>NETSDK1138</NoWarn>         </PropertyGroup>          <!-- Replace '#' through '$'! -->         <ItemGroup Condition="#(FrameworksLackingNullableReferenceTypeAttributes.Contains('|#(TargetFramework)|'))">           <PackageReference Include="Hafner.Compatibility.NullableReferenceTypeAttributes">             <Version>1.0.0</Version>           </PackageReference>         </ItemGroup>        </Project>        Above XML is a Visual Studio 2022 C# project file (*.csproj) that targets all the frameworks from .NET 2.0 to .NET 6.0 for the .NET flavors '.NET Framework', '.NET Core' and '.NET Standard'.        Watch out: If you copy/paste above snipet you need to replace the '#' signs through '$' signs.        I had to check it in like this as otherwise the condition got interpreted, sorry about that.
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