System.Runtime.Versioning.UnsupportedOSPlatformAttribute sealed class UnsupportedOSPlatformAttribute : Attribute Polyfill for UnsupportedOSPlatformAttribute which is only available in .NET 5+. Marks APIs that are unsupported on a given platform. Documentation Code public string PlatformName { get; } public UnsupportedOSPlatformAttribute(string platformName)