.NET MAUI项目CA1416警告与NETSDK1135错误解决咨询

项目背景 #

我有一个规模较大的.NET MAUI项目，其中包含多个基于.NET 6的私有包，这些包的框架定义直接使用模板生成：

<TargetFramework>net6.0</TargetFramework>
<TargetFrameworks>net6.0;net6.0-android;net6.0-ios;net6.0-maccatalyst</TargetFrameworks>

构建警告问题 #

构建该MAUI应用时，收到大量CA1416警告示例如下：

3>C:\Maui\MauiProgram.cs(94,13,97,78): warning CA1416: This call site is reachable on: 'iOS' 15.4 and later, 'maccatalyst' 15.4 and later. 'TokenRetrievalHandler<SignInPolicy>' is only supported on: 'iOS' 16.0 and later, 'maccatalyst' 16.0 and later.
3>C:\Maui\MauiProgram.cs(89,13,91,93): warning CA1416: This call site is reachable on: 'iOS' 15.4 and later, 'maccatalyst' 15.4 and later. 'MsalTokenService<SignInPolicy>' is only supported on: 'iOS' 16.0 and later, 'maccatalyst' 16.0 and later.
3>C:\Maui\MauiProgram.cs(89,13,91,93): warning CA1416: This call site is reachable on: 'iOS' 15.4 and later, 'maccatalyst' 15.4 and later. 'ITokenService<SignInPolicy>' is only supported on: 'iOS' 16.0 and later, 'maccatalyst' 16.0 and later.
3>C:\Maui\MauiProgram.cs(96,52,96,100): warning CA1416: This call site is reachable on: 'iOS' 15.4 and later, 'maccatalyst' 15.4 and later. 'Policy.TokenRefresher<SignInPolicy>(IServiceProvider, HttpRequestMessage)' is only supported on: 'iOS' 16.0 and later, 'maccatalyst' 16.0 and later.
3>C:\Maui\MauiProgram.cs(101,13,104,37): warning CA1416: This call site is reachable on: 'iOS' 15.4 and later, 'maccatalyst' 15.4 and later. 'ServiceCollectionExtensions.UseThetaRexCommon(IServiceCollection)' is only supported on: 'iOS' 16.0 and later, 'maccatalyst' 16.0 and later.
3>C:\Maui\MauiProgram.cs(89,13,90,69): warning CA1416: This call site is reachable on: 'iOS' 15.4 and later, 'maccatalyst' 15.4 and later. 'TokenRetrievalHandler<SignInPolicy>' is only supported on: 'iOS' 16.0 and later, 'maccatalyst' 16.0 and later.
3>C:\Maui\MauiProgram.cs(95,35,95,49): warning CA1416: This call site is reachable on: 'iOS' 15.4 and later, 'maccatalyst' 15.4 and later. 'Policy.Retry()' is only supported on: 'iOS' 16.0 and later, 'maccatalyst' 16.0 and later.

所有包和MAUI项目代码中都未指定要求macCatalyst 16.0，且无法降低框架支持版本，因此尝试提高项目支持的OS版本。

修改版本后的错误 #

查看MAUI项目文件，发现默认配置如下：

<SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'ios'">15.4</SupportedOSPlatformVersion>
<SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'maccatalyst'">15.4</SupportedOSPlatformVersion>
<SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'android'">31.0</SupportedOSPlatformVersion>
<SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'windows'">10.0.17763.0</SupportedOSPlatformVersion>

将iOS的支持版本修改为16.0：

<SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'ios'">16.0</SupportedOSPlatformVersion>

此时出现构建错误：

error NETSDK1135: SupportedOSPlatformVersion 16.0 cannot be higher than TargetPlatformVersion 15.4.

但我从未手动指定过TargetPlatformVersion为15.4。

补充说明 #

奇怪的是，若将包直接作为.NET Core 6库添加到项目中，不会出现这些错误，仅当打包后才会触发问题。

内容的提问来源于stack exchange，提问作者user365462