项目文件.csproj文件内容如下:
重点是:不能有其他的
netstandard2;net40;net45;net46;net6
<Project Sdk="Microsoft.NET.Sdk"><PropertyGroup><TargetFrameworks>netstandard2;net40;net45;net46;net6</TargetFrameworks></PropertyGroup><ItemGroup Condition="'$(TargetFramework)'=='net40' OR '$(TargetFramework)'=='net45' OR '$(TargetFramework)'=='net46'"><Reference Include="System" /><Reference Include="System.Core" /><Reference Include="Microsoft.CSharp" /><Reference Include="System.Data" /></ItemGroup><ItemGroup Condition="'$(TargetFramework)'=='net45' OR '$(TargetFramework)'=='net46'"><Reference Include="System.ComponentModel.DataAnnotations" /></ItemGroup><ItemGroup><Folder Include="Http\" /><Folder Include="Log\" /><Folder Include="Ftp\" /><Folder Include="File\" /><Folder Include="EncryDecry\" /><Folder Include="FileZip\" /></ItemGroup></Project>