Add platform-specific attributes

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

@@ -0,0 +1,44 @@
+// 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 minimum platform that is required in order to the marked thing.
+    /// <list type="bullet">
+    /// <item>
+    /// <description>When applied to an assembly, it means the entire assembly cannot be called
+    /// into on earlier versions. It records the TargetPlatformMinVersion property.</description>
+    /// </item>
+    /// <item>
+    /// <description> When applied to an API, it means the API cannot be called from an earlier
+    /// version.</description>
+    /// </item>
+    /// </list>
+    ///
+    /// In either case, the caller can either mark itself with MinimumPlatformAttribute
+    /// or guard the call with a platform check.
+    ///
+    /// The attribute can be applied multiple times for different operating systems.
+    /// That means the API is supported on multiple operating systems.
+    ///
+    /// A given platform should only be specified once.
+    /// </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 MinimumOSAttribute : PlatformAttribute
+    {
+        public MinimumOSAttribute(string platformName) : base(platformName)
+        {
+        }
+    }
+}

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

@@ -0,0 +1,33 @@
+// 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 ObsoletedInPlatformAttribute : PlatformAttribute
+    {
+        public ObsoletedInPlatformAttribute(string platformName, string url, string message) : base(platformName)
+        {
+            Url = url;
+            Message = message;
+        }
+
+        public string Url { get; set; }
+        public string Message { get; }
+    }
+}

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

@@ -0,0 +1,20 @@
+// 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 attributes. Primarily used to allow grouping
+    /// in documentation.
+    /// </summary>
+    public abstract class PlatformAttribute : Attribute
+    {
+        internal PlatformAttribute(string platformName)
+        {
+            PlatformName = platformName;
+        }
+        public string PlatformName { get; }
+    }
+}

src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/RemovedInPlatformAttribute.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.
+    ///
+    /// Primarily used by OS bindings to indicate APIs that are only available 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 RemovedInPlatformAttribute : PlatformAttribute
+    {
+        public RemovedInPlatformAttribute(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 : PlatformAttribute
+    {
+        public TargetPlatformAttribute(string platformName) : base(platformName)
+        {
+        }
+    }
+}