net481 
namespace Microsoft.AspNetCore.SystemWebAdapters
{
    public class RemoteAppServerOptions
    {
        [Required]
        public string! ApiKey { get; set; }
    }
}
.NET Framework
4.7.24.84.8.1
Information specific to net481
Assembly

Microsoft.AspNetCore.SystemWebAdapters.FrameworkServices , Version=2.2.1.0, PublicKeyToken=adb9793829ddae60

Referencing

Your project needs a package reference to Microsoft.AspNetCore.SystemWebAdapters.FrameworkServices.

Package Microsoft.AspNetCore.SystemWebAdapters.FrameworkServices (2.2.1) net472
Platform Restrictions

This framework does not have platform annotations.

  • Built-in API
  • Package-provided API