While porting the library I ended up updating quite a few projects to make sure they continue to work.

There were a couple of changes to the build system that are included in this change:
     - The location of the tool to restore the packages is set to use dnu for now.
     - When restoring packages for the internal build we need to actually pass the right parameters to the build of the depproj

There were a couple of places where we had some issues that I fixed while I was doing the port:
     - The compiler gave error messages about some method out parameters not being assigned.
     - There was one missing 'unsafe' modifier on an interop file
     - I had to pull in a 'debug' method temporarily in the ret build. This was needed because the debug build of CoreLib currently does not build with the 'DEBUG' define.

[tfs-changeset: 1559864]

3 files changed, 142 insertions, 0 deletions

diff --git a/src/Common/src/System/Collections/Generic/Empty.cs b/src/Common/src/System/Collections/Generic/Empty.cs
new file mode 100644
index 000000000..b88c594b4
--- /dev/null
+++ b/src/Common/src/System/Collections/Generic/Empty.cs
@@ -0,0 +1,66 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Diagnostics;
+using System.Collections;
+using System.Collections.Generic;
+
+namespace System.Collections.Generic
+{
+    //
+    // Helper class to store reusable empty IEnumerables.
+    //
+    internal static class Empty<T>
+    {
+        //
+        // Returns a reusable empty IEnumerable<T> (that does not secretly implement more advanced collection interfaces.)
+        //
+        public static IEnumerable<T> Enumerable
+        {
+            get
+            {
+                return _enumerable;
+            }
+        }
+
+        private sealed class EmptyEnumImpl : IEnumerable<T>, IEnumerator<T>
+        {
+            public IEnumerator<T> GetEnumerator()
+            {
+                return this;
+            }
+
+            IEnumerator IEnumerable.GetEnumerator()
+            {
+                return this;
+            }
+
+            public T Current
+            {
+                get { throw new InvalidOperationException(); }
+            }
+
+            Object IEnumerator.Current
+            {
+                get { throw new InvalidOperationException(); }
+            }
+
+            public bool MoveNext()
+            {
+                return false;
+            }
+
+            public void Reset()
+            {
+            }
+
+            public void Dispose()
+            {
+            }
+        }
+
+        private static IEnumerable<T> _enumerable = new EmptyEnumImpl();
+    }
+}
+
diff --git a/src/Common/src/System/Collections/Generic/EnumerableExtensions.cs b/src/Common/src/System/Collections/Generic/EnumerableExtensions.cs
new file mode 100644
index 000000000..851b8e90a
--- /dev/null
+++ b/src/Common/src/System/Collections/Generic/EnumerableExtensions.cs
@@ -0,0 +1,22 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Diagnostics;
+using System.Collections.Generic;
+
+namespace System.Collections.Generic
+{
+    internal static class EnumerableExtensions
+    {
+        // Used to prevent returning values out of IEnumerable<>-typed properties
+        // that an untrusted caller could cast back to array or List.
+        public static IEnumerable<T> AsNothingButIEnumerable<T>(this IEnumerable<T> en)
+        {
+            foreach (T t in en)
+                yield return t;
+        }
+    }
+}
+
+
diff --git a/src/Common/src/System/Linq/LowLevelEnumerable.cs b/src/Common/src/System/Linq/LowLevelEnumerable.cs
new file mode 100644
index 000000000..2a360cb5b
--- /dev/null
+++ b/src/Common/src/System/Linq/LowLevelEnumerable.cs
@@ -0,0 +1,54 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Diagnostics;
+using System.Collections.Generic;
+
+namespace System.Linq
+{
+    internal static class LowLevelEnumerable
+    {
+        public static bool Any<T>(this IEnumerable<T> values)
+        {
+            Debug.Assert(values != null);
+
+            IEnumerator<T> enumerator = values.GetEnumerator();
+            return enumerator.MoveNext();
+        }
+
+        public static bool Any<T>(this IEnumerable<T> values, Func<T, bool> predicate)
+        {
+            Debug.Assert(values != null);
+            Debug.Assert(predicate != null);
+            foreach (T value in values)
+            {
+                if (predicate(value))
+                    return true;
+            }
+            return false;
+        }
+
+        public static IEnumerable<U> Select<T, U>(this IEnumerable<T> values, Func<T, U> func)
+        {
+            Debug.Assert(values != null);
+
+            foreach (T value in values)
+            {
+                yield return func(value);
+            }
+        }
+
+        public static T[] ToArray<T>(this IEnumerable<T> values)
+        {
+            Debug.Assert(values != null);
+
+            LowLevelList<T> list = new LowLevelList<T>();
+            foreach (T value in values)
+            {
+                list.Add(value);
+            }
+            return list.ToArray();
+        }
+    }
+}