Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

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

@@ -0,0 +1,30 @@
+//------------------------------------------------------------
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+//------------------------------------------------------------
+
+namespace System.IdentityModel
+{
+    class ExtendedTransformFactory : StandardTransformFactory
+    {
+        static ExtendedTransformFactory instance = new ExtendedTransformFactory();
+
+        ExtendedTransformFactory() { }
+
+        internal new static ExtendedTransformFactory Instance
+        {
+            get { return instance; }
+        }
+
+        public override Transform CreateTransform(string transformAlgorithmUri)
+        {
+            if (transformAlgorithmUri == XD.XmlSignatureDictionary.EnvelopedSignature.Value)
+            {
+                return new EnvelopedSignatureTransform();
+            }
+            else
+            {
+                return base.CreateTransform(transformAlgorithmUri);
+            }
+        }
+    }
+}