MacOS下dotnet build找不到Xamarin targets及rzc.dll缺失问题求助

一、终端执行dotnet build提示找不到Xamarin targets文件 #

报错信息 #

/path/to/repo/Toolkit/My.Company.Toolkit.Platform.Android/My.Company.Toolkit.Platform.Android.csproj(91,3): error MSB4019: The imported project "/usr/local/share/dotnet/sdk/7.0.102/Xamarin/Android/Xamarin.Android.CSharp.targets" was not found. Confirm that the expression in the Import declaration "/usr/local/share/dotnet/sdk/7.0.102//Xamarin/Android/Xamarin.Android.CSharp.targets" is correct, and that the file exists on disk.
/path/to/repo/Toolkit/My.Company.Toolkit.Platform.iOS/My.Company.Toolkit.Platform.iOS.csproj(195,3): error MSB4019: The imported project "/usr/local/share/dotnet/sdk/7.0.102/Xamarin/iOS/Xamarin.iOS.CSharp.targets" was not found. Confirm that the expression in the Import declaration "/usr/local/share/dotnet/sdk/7.0.102//Xamarin/iOS/Xamarin.iOS.CSharp.targets" is correct, and that the file exists on disk.

原因 #

系统级dotnet SDK（路径/usr/local/share/dotnet/sdk）不包含Xamarin的MSBuild targets文件，Xamarin组件的targets实际存放在Visual Studio for Mac的安装目录中。终端直接调用dotnet build时，无法正确解析$(MSBuildExtensionsPath)变量指向VS的Xamarin路径。

解决办法 #

1. 使用Visual Studio自带的MSBuild构建
   直接调用VS内置的MSBuild来执行构建，确保路径指向正确：

dotnet exec "/Applications/Visual Studio.app/Contents/MacOS/MSBuild/bin/MSBuild.dll" /path/to/your/solution.sln

2. 手动设置MSBuildExtensionsPath环境变量
   在终端临时设置环境变量，让dotnet build能找到Xamarin的targets文件：

export MSBuildExtensionsPath="/Applications/Visual Studio.app/Contents/Resources/lib/monodevelop/bin/MSBuild"
dotnet build /path/to/your/solution.sln

二、重装VS后，VS内构建提示rzc.dll不存在 #

报错信息 #

Target RazorGenerateComponentDeclaration:
    /usr/local/share/dotnet/dotnet exec "/Users/redacted/Library/Caches/VisualStudio/17.0/MSBuild/36265_3/Sdks/Microsoft.NET.Sdk.Razor/build/netstandard2.0/../../tools/netcoreapp3.0/rzc.dll" generate
    ...
    The application to execute does not exist: '/Users/redacted/Library/Caches/VisualStudio/17.0/MSBuild/36265_3/Sdks/Microsoft.NET.Sdk.Razor/build/netstandard2.0/../../tools/netcoreapp3.0/rzc.dll'
    /Users/redacted/Library/Caches/VisualStudio/17.0/MSBuild/36265_3/Sdks/Microsoft.NET.Sdk.Razor/build/netstandard2.0/Microsoft.NET.Sdk.Razor.Component.targets(106,5): error : rzc generate exited with code 129.

原因 #

VS缓存的Razor SDK文件损坏或缺失，或者项目依赖的.NET Core 3.0 runtime未安装（rzc.dll需要该runtime环境）。

解决办法 #

1. 清理VS的MSBuild缓存
   删除VS的MSBuild缓存目录，重启VS后会自动重新下载正确的SDK文件：

rm -rf /Users/$(whoami)/Library/Caches/VisualStudio/17.0/MSBuild

重启Visual Studio for Mac后再尝试构建。

2. 安装.NET Core 3.0 Runtime
   rzc.dll依赖.NET Core 3.0 runtime，虽然你的dotnet --info未显示该版本，但需要手动安装对应架构（arm64）的.NET Core 3.0 runtime。安装完成后重启VS再构建。

3. 更新Razor SDK版本
   检查项目中Microsoft.NET.Sdk.Razor的版本，尝试升级到兼容项目.NET版本的包（比如项目用netstandard2.1，可升级到3.1.x及以上版本），避免依赖过旧的netcoreapp3.0版本的rzc工具。

内容的提问来源于stack exchange，提问作者grandouassou