Merge pull request #45 from dotnet-campus/t/walterlv/net6

支持 .NET 6.0 并且只在 .NET8.0 上产生警告

Author: lindexi

src/DotNetCampus.CommandLine/DotNetCampus.CommandLine.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFrameworks>net8.0;net6.0</TargetFrameworks>
     <ImplicitUsings>enable</ImplicitUsings>
     <PackageId>dotnetCampus.CommandLine</PackageId>
     <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
@@ -11,6 +11,7 @@
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
     <EmbedAllSources Condition="'$(Configuration)' != 'debug'">true</EmbedAllSources>
+    <WarningLevel Condition="'$(TargetFramework)' == 'net6.0'">0</WarningLevel>
   </PropertyGroup>
 
   <ItemGroup>
@@ -22,6 +23,7 @@
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
+    <PackageReference Condition="'$(TargetFramework)' == 'net6.0'" Include="System.Collections.Immutable" Version="8.0.0" />
   </ItemGroup>
 
   <Target Name="_IncludeAllDependencies" BeforeTargets="_GetPackageFiles">

src/DotNetCampus.CommandLine/Utils/CommandLineValueConverter.cs

@@ -82,6 +82,7 @@ internal static bool ArgumentStringsToBoolean(ImmutableArray<string>? arguments)
         }
     }
 
+#if NET8_0_OR_GREATER
     private static T? ArgumentStringsToValue<T>(ImmutableArray<string>? arguments) where T : IParsable<T> => arguments switch
     {
         null or { Length: 0 } => default,
@@ -90,6 +91,7 @@ internal static bool ArgumentStringsToBoolean(ImmutableArray<string>? arguments)
             : throw new CommandLineParseValueException(
                 $"Value [{values[0]}] is not a valid value for type {typeof(T).Name}."),
     };
+#endif
 
     internal static byte ArgumentStringsToByte(ImmutableArray<string>? arguments) => arguments switch
     {