Add platform-specific attributes

src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/MinimumOSPlatformAttribute.cs

@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    /// <summary>
+    /// Records the operating system (and minimum version) that supports an API. Multiple attributes can be
+    /// applied to indicate support on multiple operating systems.
+    /// </summary>
+    /// <remarks>
+    /// Callers can apply a <see cref="System.Runtime.InteropServices.MinimumOSPlatformAttribute" />
+    /// or use guards to prevent calls to APIs on unsupported operating systems.
+    ///
+    /// A given platform should only be specified once.
+    /// </remarks>
+    [AttributeUsage(AttributeTargets.Assembly |
+                    AttributeTargets.Class |
+                    AttributeTargets.Constructor |
+                    AttributeTargets.Event |
+                    AttributeTargets.Method |
+                    AttributeTargets.Module |
+                    AttributeTargets.Property |
+                    AttributeTargets.Struct,
+                    AllowMultiple = true, Inherited = false)]
+    public sealed class MinimumOSPlatformAttribute : OSPlatformAttribute
+    {
+        public MinimumOSPlatformAttribute(string platformName) : base(platformName)
+        {
+        }
+    }
+}

src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/OSPlatformAttribute.cs

@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    /// <summary>
+    /// Base type for all platform-specific API attributes.
+    /// </summary>
+    public abstract class OSPlatformAttribute : Attribute
+    {
+        private protected OSPlatformAttribute(string platformName)
+        {
+            PlatformName = platformName;
+        }
+        public string PlatformName { get; }
+    }
+}

src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/ObsoletedInOSPlatformAttribute.cs

@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    /// <summary>
+    /// Marks APIs that were obsoleted in a given operating system version.
+    ///
+    /// Primarily used by OS bindings to indicate APIs that should only be used in
+    /// earlier versions.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Assembly |
+                    AttributeTargets.Class |
+                    AttributeTargets.Constructor |
+                    AttributeTargets.Event |
+                    AttributeTargets.Method |
+                    AttributeTargets.Module |
+                    AttributeTargets.Property |
+                    AttributeTargets.Struct,
+                    AllowMultiple = true, Inherited = false)]
+    public sealed class ObsoletedInOSPlatformAttribute : OSPlatformAttribute
+    {
+        public ObsoletedInOSPlatformAttribute(string platformName) : base(platformName)
+        {
+        }
+
+        public ObsoletedInOSPlatformAttribute(string platformName, string message) : base(platformName)
+        {
+            Message = message;
+        }
+
+        public string Message { get; }
+        public string Url { get; set; }
+    }
+}

src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/RemovedInOSPlatformAttribute.cs

@@ -0,0 +1,29 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    /// <summary>
+    /// Marks APIs that were removed in a given operating system version.
+    /// </summary>
+    /// <remarks>
+    /// Primarily used by OS bindings to indicate APIs that are only available in
+    /// earlier versions.
+    /// </remarks>
+    [AttributeUsage(AttributeTargets.Assembly |
+                    AttributeTargets.Class |
+                    AttributeTargets.Constructor |
+                    AttributeTargets.Event |
+                    AttributeTargets.Method |
+                    AttributeTargets.Module |
+                    AttributeTargets.Property |
+                    AttributeTargets.Struct,
+                    AllowMultiple = true, Inherited = false)]
+    public sealed class RemovedInOSPlatformAttribute : OSPlatformAttribute
+    {
+        public RemovedInOSPlatformAttribute(string platformName) : base(platformName)
+        {
+        }
+    }
+}

src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/TargetPlatformAttribute.cs

@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Runtime.InteropServices
+{
+    /// <summary>
+    /// Records the platform that the project targeted.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Assembly,
+                    AllowMultiple = false, Inherited = false)]
+    public sealed class TargetPlatformAttribute : OSPlatformAttribute
+    {
+        public TargetPlatformAttribute(string platformName) : base(platformName)
+        {
+        }
+    }
+}