Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.Activities/System/Activities/Validation/GetWorkflowTree.cs

@@ -0,0 +1,39 @@
+//-----------------------------------------------------------------------------
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+//-----------------------------------------------------------------------------
+
+namespace System.Activities.Validation
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Runtime;   
+
+    public sealed class GetWorkflowTree : CodeActivity<IEnumerable<Activity>>
+    {
+        public GetWorkflowTree()
+            : base()
+        {
+        }
+
+        public InArgument<ValidationContext> ValidationContext
+        {
+            get;
+            set;
+        }
+
+        protected override IEnumerable<Activity> Execute(CodeActivityContext context)
+        {
+            Fx.Assert(this.ValidationContext != null, "ValidationContext must not be null");
+
+            ValidationContext currentContext = this.ValidationContext.Get(context);
+            if (currentContext != null)
+            {
+                return currentContext.GetWorkflowTree();
+            }
+            else
+            {
+                return ActivityValidationServices.EmptyChildren;
+            }
+        }
+    }
+}