# System.Runtime.Versioning

``` diff
 namespace System.Runtime.Versioning {
+    public sealed class RequiresPreviewFeaturesAttribute : Attribute {
+        public RequiresPreviewFeaturesAttribute();
+    }
+    public sealed class SupportedOSPlatformGuardAttribute : OSPlatformAttribute {
+        public SupportedOSPlatformGuardAttribute(string platformName);
+    }
+    public sealed class UnsupportedOSPlatformGuardAttribute : OSPlatformAttribute {
+        public UnsupportedOSPlatformGuardAttribute(string platformName);
+    }
 }
```

