Csharp 处理. netstandard2.0项目中HttpClient.SslProtocol的PlatformNotSupportedException问题""

我有两个项目使用的.netstandard2.0项目.一个是. net核心项目，一个是. netframework4.7.1.当我在.netframework4.7.1中引用我的.Netstandard2.0项目时，我得到了HttpClient.sslProtocol的"PlatformNotSupportedException".我知道在.netframework4.7.1中不支持它，但我想跳过代码.netframework4.7.1，不要跳过. netcore.我如何在.netstansard2.0中处理这个问题？ 我无法访问.netframework4.7.1和. net核心.我只能访问.netstandard2.0，其中"HttpClient.sslProtocol"使用.我可以在.netframework4.7.1和. net core中做任何事情.我可以在.netstandard2.0中做什么？ 在. netcore.netcore.com中运行良好.

这是我的密码

    private static readonly HttpClient _httpClient = new HttpClient(new HttpClientHandler() { 
        AutomaticDecompression = System.Net.DecompressionMethods.GZip | System.Net.DecompressionMethods.Deflate, 
        ServerCertificateCustomValidationCallback = null, 
        SslProtocols = System.Security.Authentication.SslProtocols.Tls11 
    })
    {
        Timeout = TimeSpan.FromSeconds(45)
    };

以下代码是实现ihttpclientfactory时的代码

    private static readonly Lazy<IHttpClientFactory> httpClientFactoryLazy = new Lazy<IHttpClientFactory>(() =>
    {
        var services = new ServiceCollection();
        services.AddHttpClient("HttpClientFactory", client =>
        {
            client.Timeout = TimeSpan.FromSeconds(15);
        })
          .ConfigurePrimaryHttpMessageHandler(() =>
          {
              var handler = new HttpClientHandler();
              handler.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
              handler.SslProtocols = System.Security.Authentication.SslProtocols.Tls11;
              return handler;
          });
        var serviceProvider = services.BuildServiceProvider();
        return serviceProvider.GetRequiredService<IHttpClientFactory>();
    });

我们可以使用下面的代码识别框架版本并相应地执行代码吗？

private string getCallingFramework() {

    return RuntimeInformation.FrameworkDescription;
}