Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Runtime.Caching/System/Caching/SafeRegistryHandle.cs

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+// <copyright file="SafeRegistryHandle.cs" company="Microsoft">
+//   Copyright (c) 2009 Microsoft Corporation.  All rights reserved.
+// </copyright>
+using Microsoft.Win32;
+using Microsoft.Win32.SafeHandles;
+using System;
+using System.Security;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace System.Runtime.Caching {
+    [SecurityCritical]
+    internal class SafeRegistryHandle : SafeHandleZeroOrMinusOneIsInvalid {
+        // Note: Officially -1 is the recommended invalid handle value for
+        // registry keys, but we'll also get back 0 as an invalid handle from
+        // RegOpenKeyEx.
+        
+        [ResourceExposure(ResourceScope.Machine)]
+        internal SafeRegistryHandle() : base(true) {}
+        
+        [SecurityCritical]
+        protected override bool ReleaseHandle() {
+            // Returns a Win32 error code, 0 for success
+#if MONO
+            throw new NotImplementedException ();
+#else
+            int r = UnsafeNativeMethods.RegCloseKey(handle);
+            return r == 0;
+#endif
+        }
+    }
+}