Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.IdentityModel/System/IdentityModel/SecurityUniqueId.cs

@@ -0,0 +1,47 @@
+//------------------------------------------------------------
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+//------------------------------------------------------------
+
+namespace System.IdentityModel
+{
+    using System.Globalization;
+    using System.Threading;
+
+    class SecurityUniqueId
+    {
+        static long nextId = 0;
+        static string commonPrefix = "uuid-" + Guid.NewGuid().ToString() + "-";
+
+        long id;
+        string prefix;
+        string val;
+
+        SecurityUniqueId(string prefix, long id)
+        {
+            this.id = id;
+            this.prefix = prefix;
+            this.val = null;
+        }
+
+        public static SecurityUniqueId Create()
+        {
+            return SecurityUniqueId.Create(commonPrefix);
+        }
+
+        public static SecurityUniqueId Create(string prefix)
+        {
+            return new SecurityUniqueId(prefix, Interlocked.Increment(ref nextId));
+        }
+
+        public string Value
+        {
+            get
+            {
+                if (this.val == null)
+                    this.val = this.prefix + this.id.ToString(CultureInfo.InvariantCulture);
+
+                return this.val;
+            }
+        }
+    }
+}