diff --git a/Src/Compilers/Core/Portable/CodeAnalysis.csproj b/Src/Compilers/Core/Portable/CodeAnalysis.csproj
index 6e16ed76da86621a9a9e54af29c7ba215374896f..d3bd221b9551190cdff8bdbf2fbe50e423953f0a 100644
--- a/Src/Compilers/Core/Portable/CodeAnalysis.csproj
+++ b/Src/Compilers/Core/Portable/CodeAnalysis.csproj
@@ -113,6 +113,7 @@
     <Compile Include="Collections\ImmutableArrayExtensions.cs" />
     <Compile Include="Collections\ImmutableMemoryStream.cs" />
     <Compile Include="Collections\OrderedSet.cs" />
+    <Compile Include="Collections\StaticCast.cs" />
     <Compile Include="Compilation\SymbolFilter.cs" />
     <Compile Include="DiagnosticAnalyzer\CompilerDiagnosticAnalyzer.CompilationAnalyzer.cs" />
     <Compile Include="DiagnosticAnalyzer\CompilerDiagnosticAnalyzer.cs" />
@@ -265,7 +266,6 @@
     <Compile Include="InternalUtilities\ISetExtensions.cs" />
     <Compile Include="InternalUtilities\KeyValuePair.cs" />
     <Compile Include="InternalUtilities\MultiDictionary.cs" />
-    <Compile Include="InternalUtilities\ObjectPool`1.cs" />
     <Compile Include="InternalUtilities\OneOrMany.cs" />
     <Compile Include="InternalUtilities\ReaderWriterLockSlimExtensions.cs" />
     <Compile Include="InternalUtilities\ReadOnlyUnmanagedMemoryStream.cs" />
diff --git a/Src/Compilers/Core/Portable/Collections/ImmutableArrayExtensions.cs b/Src/Compilers/Core/Portable/Collections/ImmutableArrayExtensions.cs
index c399c18b3847cc969ff1edfccd5b026aa79084cc..8f88511fead08091777a7f8b16e926dd6e98b2e0 100644
--- a/Src/Compilers/Core/Portable/Collections/ImmutableArrayExtensions.cs
+++ b/Src/Compilers/Core/Portable/Collections/ImmutableArrayExtensions.cs
@@ -6,16 +6,14 @@
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
-using System.Reflection;
 using System.Runtime.CompilerServices;
-using System.Runtime.InteropServices;
 
 namespace Microsoft.CodeAnalysis
 {
     /// <summary>
     /// The collection of extension methods for the <see cref="ImmutableArray{T}"/> type
     /// </summary>
-    public static partial class ImmutableArrayExtensions
+    internal static class ImmutableArrayExtensions
     {
         /// <summary>
         /// Converts a sequence to an immutable array.
@@ -213,11 +211,13 @@ public static ImmutableArray<T> WhereAsArray<T>(this ImmutableArray<T> array, Fu
                     {
                         continue;
                     }
+
                     Debug.Assert(i > 0);
                     if (builder == null)
                     {
                         builder = ArrayBuilder<T>.GetInstance();
                     }
+
                     builder.Add(a);
                 }
                 else
@@ -227,6 +227,7 @@ public static ImmutableArray<T> WhereAsArray<T>(this ImmutableArray<T> array, Fu
                         all = false;
                         continue;
                     }
+
                     Debug.Assert(i > 0);
                     if (all)
                     {
@@ -258,30 +259,9 @@ public static ImmutableArray<T> WhereAsArray<T>(this ImmutableArray<T> array, Fu
             }
         }
 
-        /// <summary>
-        /// Adds all elements of the immutable array into the list; The list must not be null.
-        /// </summary>
-        /// <typeparam name="T"></typeparam>
-        /// <typeparam name="U"></typeparam>
-        /// <param name="list"></param>
-        /// <param name="items"></param>
-        public static void AddRange<T, U>(this List<T> list, ImmutableArray<U> items) where U : T
-        {
-            Debug.Assert(list != null);
-
-            foreach (var u in items)
-            {
-                list.Add(u);
-            }
-        }
-
         /// <summary>
         /// Casts the immutable array of a Type to an immutable array of its base type.
         /// </summary>
-        /// <typeparam name="TDerived"></typeparam>
-        /// <typeparam name="TBase"></typeparam>
-        /// <param name="items"></param>
-        /// <returns></returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static ImmutableArray<TBase> Cast<TDerived, TBase>(this ImmutableArray<TDerived> items)
             where TDerived : class, TBase
@@ -311,7 +291,7 @@ public static bool SetEquals<T>(this ImmutableArray<T> array1, ImmutableArray<T>
             var count1 = array1.Length;
             var count2 = array2.Length;
 
-            //avoid constructing HashSets in these common cases
+            // avoid constructing HashSets in these common cases
             if (count1 == 0)
             {
                 return count2 == 0;
@@ -338,9 +318,6 @@ public static bool SetEquals<T>(this ImmutableArray<T> array1, ImmutableArray<T>
         /// <summary>
         /// Returns an empty array if the input array is null (defaut)
         /// </summary>
-        /// <typeparam name="T"></typeparam>
-        /// <param name="array"></param>
-        /// <returns></returns>
         public static ImmutableArray<T> NullToEmpty<T>(this ImmutableArray<T> array)
         {
             return array.IsDefault ? ImmutableArray<T>.Empty : array;
@@ -350,10 +327,6 @@ public static ImmutableArray<T> NullToEmpty<T>(this ImmutableArray<T> array)
         /// Returns an array of distinct elements, preserving the order in the original array.
         /// If the array has no duplicates, the original array is returned. The original array must not be null.
         /// </summary>
-        /// <typeparam name="T"></typeparam>
-        /// <param name="array"></param>
-        /// <param name="comparer"></param>
-        /// <returns></returns>
         public static ImmutableArray<T> Distinct<T>(this ImmutableArray<T> array, IEqualityComparer<T> comparer = null)
         {
             Debug.Assert(!array.IsDefault);
@@ -447,13 +420,18 @@ internal static bool HasDuplicates<T>(this ImmutableArray<T> array, IEqualityCom
                 case 0:
                 case 1:
                     return false;
+
                 case 2:
                     return comparer.Equals(array[0], array[1]);
+
                 default:
                     var set = new HashSet<T>(comparer);
                     foreach (var i in array)
                     {
-                        if (!set.Add(i)) return true;
+                        if (!set.Add(i))
+                        {
+                            return true;
+                        }
                     }
 
                     return false;
@@ -475,15 +453,8 @@ public static int Count<T>(this ImmutableArray<T> items, Func<T, bool> predicate
                     ++count;
                 }
             }
-            return count;
-        }
-    }
 
-    internal static class StaticCast<T>
-    {
-        internal static ImmutableArray<T> From<TDerived>(ImmutableArray<TDerived> from) where TDerived : class, T
-        {
-            return ImmutableArray.Create<T, TDerived>(from);
+            return count;
         }
     }
 }
diff --git a/Src/Compilers/Core/Portable/Collections/StaticCast.cs b/Src/Compilers/Core/Portable/Collections/StaticCast.cs
new file mode 100644
index 0000000000000000000000000000000000000000..3191bfadefbb38c93c7b70c2be549a8f56d4aee8
--- /dev/null
+++ b/Src/Compilers/Core/Portable/Collections/StaticCast.cs
@@ -0,0 +1,14 @@
+// Copyright (c) Microsoft Open Technologies, Inc.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+using System.Collections.Immutable;
+
+namespace Microsoft.CodeAnalysis
+{
+    internal static class StaticCast<T>
+    {
+        internal static ImmutableArray<T> From<TDerived>(ImmutableArray<TDerived> from) where TDerived : class, T
+        {
+            return ImmutableArray.Create<T, TDerived>(from);
+        }
+    }
+}
diff --git a/Src/Compilers/Core/Portable/InternalUtilities/ObjectPool`1.cs b/Src/Compilers/Core/SharedCollections/ObjectPool`1.cs
similarity index 100%
rename from Src/Compilers/Core/Portable/InternalUtilities/ObjectPool`1.cs
rename to Src/Compilers/Core/SharedCollections/ObjectPool`1.cs
diff --git a/Src/Compilers/Core/SharedCollections/SharedCollections.projitems b/Src/Compilers/Core/SharedCollections/SharedCollections.projitems
index 681878550047e24fe19935994e74af4b4abb0578..4939d9a867e6f78def3ad137018d02854f1e4440 100644
--- a/Src/Compilers/Core/SharedCollections/SharedCollections.projitems
+++ b/Src/Compilers/Core/SharedCollections/SharedCollections.projitems
@@ -15,6 +15,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)ArrayBuilder.Enumerator.cs">
       <ExcludeFromStyleCop>true</ExcludeFromStyleCop>
     </Compile>
+    <Compile Include="$(MSBuildThisFileDirectory)ObjectPool`1.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)PooledDictionary.cs">
       <ExcludeFromStyleCop>true</ExcludeFromStyleCop>
     </Compile>
diff --git a/Src/Test/PdbUtilities/PdbUtilities.csproj b/Src/Test/PdbUtilities/PdbUtilities.csproj
index 0214629e69d0488775717322bd94a97271545d48..d79f5896f89267c2d792da28c5ea9cf20adbc282 100644
--- a/Src/Test/PdbUtilities/PdbUtilities.csproj
+++ b/Src/Test/PdbUtilities/PdbUtilities.csproj
@@ -26,9 +26,6 @@
     <Compile Include="..\..\Compilers\Core\Portable\InternalUtilities\ComStreamWrapper.cs">
       <Link>InternalUtilities\ComStreamWrapper.cs</Link>
     </Compile>
-    <Compile Include="..\..\Compilers\Core\Portable\InternalUtilities\ObjectPool`1.cs">
-      <Link>InternalUtilities\ObjectPool`1.cs</Link>
-    </Compile>
   </ItemGroup>
   <ItemGroup Label="File References">
     <Reference Include="..\..\..\packages\MDbg.0.1.0\lib\net40\CorApi.dll" />
diff --git a/Src/Workspaces/Core/Desktop/Workspace/Host/Mef/DesktopMefHostServices.cs b/Src/Workspaces/Core/Desktop/Workspace/Host/Mef/DesktopMefHostServices.cs
index 223dbee2eee391ea4b48199f67179e66d7cd6c52..e2fc15ed3f1d138fc0c4933fec1936fbcf910628 100644
--- a/Src/Workspaces/Core/Desktop/Workspace/Host/Mef/DesktopMefHostServices.cs
+++ b/Src/Workspaces/Core/Desktop/Workspace/Host/Mef/DesktopMefHostServices.cs
@@ -47,7 +47,7 @@ private static ImmutableArray<Assembly> CreateDefaultAssemblies()
                 "Microsoft.CodeAnalysis.VisualBasic.Workspaces.Desktop",
             };
 
-            return MefHostServices.DefaultAssemblies.Concat(MefHostServices.LoadNearbyAssemblies(assemblyNames)).ToImmutableArray();
+            return MefHostServices.DefaultAssemblies.Concat(MefHostServices.LoadNearbyAssemblies(assemblyNames));
         }
     }
 }
\ No newline at end of file
diff --git a/Src/Workspaces/Core/Portable/CodeGeneration/Symbols/CodeGenerationConstructedMethodSymbol.cs b/Src/Workspaces/Core/Portable/CodeGeneration/Symbols/CodeGenerationConstructedMethodSymbol.cs
index dfec478951fecc924a9d99a13f7f51e3a0a473d8..753e0bb6c0f07d9a1c2b0e28158524cee93cb6a5 100644
--- a/Src/Workspaces/Core/Portable/CodeGeneration/Symbols/CodeGenerationConstructedMethodSymbol.cs
+++ b/Src/Workspaces/Core/Portable/CodeGeneration/Symbols/CodeGenerationConstructedMethodSymbol.cs
@@ -55,7 +55,7 @@ public override ImmutableArray<ITypeSymbol> TypeArguments
         {
             get
             {
-                return this.typeArguments.AsImmutable();
+                return ImmutableArray.CreateRange(this.typeArguments);
             }
         }
 
diff --git a/Src/Workspaces/Core/Portable/CodeGeneration/Symbols/CodeGenerationConstructedNamedTypeSymbol.cs b/Src/Workspaces/Core/Portable/CodeGeneration/Symbols/CodeGenerationConstructedNamedTypeSymbol.cs
index 86eb3c381ee324ea99af960887ae62ca923dd10e..94355aa1dfe9ebde105509b4593dc95aa4af58aa 100644
--- a/Src/Workspaces/Core/Portable/CodeGeneration/Symbols/CodeGenerationConstructedNamedTypeSymbol.cs
+++ b/Src/Workspaces/Core/Portable/CodeGeneration/Symbols/CodeGenerationConstructedNamedTypeSymbol.cs
@@ -30,7 +30,7 @@ public override ImmutableArray<ITypeSymbol> TypeArguments
         {
             get
             {
-                return this.typeArguments.AsImmutable();
+                return ImmutableArray.CreateRange(this.typeArguments);
             }
         }
 
@@ -143,7 +143,7 @@ public override ImmutableArray<IMethodSymbol> Constructors
         public override ImmutableArray<INamedTypeSymbol> GetTypeMembers()
         {
             // TODO(cyrusn): construct these.
-            return this.constructedFrom.TypeMembers.Cast<INamedTypeSymbol>().AsImmutable();
+            return ImmutableArray.CreateRange(this.constructedFrom.TypeMembers.Cast<INamedTypeSymbol>());
         }
 
         public override TypeKind TypeKind
diff --git a/Src/Workspaces/Core/Portable/CodeGeneration/Symbols/CodeGenerationNamedTypeSymbol.cs b/Src/Workspaces/Core/Portable/CodeGeneration/Symbols/CodeGenerationNamedTypeSymbol.cs
index 6c3a90b3993e2ada7e592fd20a05aad97e08133c..caee35efd49dcfadef1dd383d0477f435341ae1c 100644
--- a/Src/Workspaces/Core/Portable/CodeGeneration/Symbols/CodeGenerationNamedTypeSymbol.cs
+++ b/Src/Workspaces/Core/Portable/CodeGeneration/Symbols/CodeGenerationNamedTypeSymbol.cs
@@ -168,7 +168,7 @@ public override ImmutableArray<ITypeParameterSymbol> TypeParameters
         {
             get
             {
-                return this.typeParameters.AsImmutable();
+                return ImmutableArray.CreateRange(this.typeParameters);
             }
         }
 
@@ -184,18 +184,18 @@ public override ImmutableArray<INamedTypeSymbol> Interfaces
         {
             get
             {
-                return this.interfaces.AsImmutable();
+                return ImmutableArray.CreateRange(this.interfaces);
             }
         }
 
         public override ImmutableArray<ISymbol> GetMembers()
         {
-            return this.members.Concat(this.TypeMembers).AsImmutable();
+            return ImmutableArray.CreateRange(this.members.Concat(this.TypeMembers));
         }
 
         public override ImmutableArray<INamedTypeSymbol> GetTypeMembers()
         {
-            return this.TypeMembers.Cast<INamedTypeSymbol>().AsImmutable();
+            return ImmutableArray.CreateRange(this.TypeMembers.Cast<INamedTypeSymbol>());
         }
 
         public override ImmutableArray<IMethodSymbol> InstanceConstructors
@@ -203,9 +203,8 @@ public override ImmutableArray<IMethodSymbol> InstanceConstructors
             get
             {
                 // NOTE(cyrusn): remember to Construct the result if we implement this.
-                return this.GetMembers().OfType<IMethodSymbol>()
-                                        .Where(m => m.MethodKind == MethodKind.Constructor && !m.IsStatic)
-                                        .AsImmutable();
+                return ImmutableArray.CreateRange(
+                    this.GetMembers().OfType<IMethodSymbol>().Where(m => m.MethodKind == MethodKind.Constructor && !m.IsStatic));
             }
         }
 
@@ -214,9 +213,8 @@ public override ImmutableArray<IMethodSymbol> StaticConstructors
             get
             {
                 // NOTE(cyrusn): remember to Construct the result if we implement this.
-                return this.GetMembers().OfType<IMethodSymbol>()
-                                        .Where(m => m.MethodKind == MethodKind.StaticConstructor && m.IsStatic)
-                                        .AsImmutable();
+                return ImmutableArray.CreateRange(
+                    this.GetMembers().OfType<IMethodSymbol>().Where(m => m.MethodKind == MethodKind.StaticConstructor && m.IsStatic));
             }
         }
 
diff --git a/Src/Workspaces/Core/Portable/Shared/Extensions/IMethodSymbolExtensions.cs b/Src/Workspaces/Core/Portable/Shared/Extensions/IMethodSymbolExtensions.cs
index c6c038bd74d12b4ec53af344395db5c8eb1b6041..d4469a865730dd51ee4cc81ea1916acdc66c43cf 100644
--- a/Src/Workspaces/Core/Portable/Shared/Extensions/IMethodSymbolExtensions.cs
+++ b/Src/Workspaces/Core/Portable/Shared/Extensions/IMethodSymbolExtensions.cs
@@ -2,6 +2,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Linq;
 using System.Threading;
 using Microsoft.CodeAnalysis;
@@ -136,8 +137,7 @@ public static IMethodSymbol RenameParameters(this IMethodSymbol method, IList<st
             // Now we update the constraints.
             foreach (var newTypeParameter in newTypeParameters)
             {
-                newTypeParameter.ConstraintTypes = newTypeParameter.ConstraintTypes.Select(
-                    t => t.SubstituteTypes(mapping, typeGenerator)).AsImmutable();
+                newTypeParameter.ConstraintTypes = ImmutableArray.CreateRange(newTypeParameter.ConstraintTypes, t => t.SubstituteTypes(mapping, typeGenerator));
             }
 
             return newTypeParameters.Cast<ITypeParameterSymbol>().ToList();
diff --git a/Src/Workspaces/Core/Portable/Shared/Extensions/ISymbolExtensions.cs b/Src/Workspaces/Core/Portable/Shared/Extensions/ISymbolExtensions.cs
index f49d71246f5dac65fd462d7bb14d297e5bccb91b..6b18789bf2150cae76ca4134399194efdf900972 100644
--- a/Src/Workspaces/Core/Portable/Shared/Extensions/ISymbolExtensions.cs
+++ b/Src/Workspaces/Core/Portable/Shared/Extensions/ISymbolExtensions.cs
@@ -427,7 +427,7 @@ public static ImmutableArray<ITypeSymbol> GetAllTypeArguments(this ISymbol symbo
                 containingType = containingType.ContainingType;
             }
 
-            return results.AsImmutable();
+            return ImmutableArray.CreateRange(results);
         }
 
         public static bool IsAttribute(this ISymbol symbol)
diff --git a/Src/Workspaces/Core/Portable/Workspaces.csproj b/Src/Workspaces/Core/Portable/Workspaces.csproj
index b7ecb91de67327cd3965e809b543f7d6ea1396ff..520974dd6f655dd4ad66c52bdd1dc2ab370a33c3 100644
--- a/Src/Workspaces/Core/Portable/Workspaces.csproj
+++ b/Src/Workspaces/Core/Portable/Workspaces.csproj
@@ -49,6 +49,9 @@
     </ProjectReference>
   </ItemGroup>
   <ItemGroup Label="Linked Files">
+    <Compile Include="..\..\..\Compilers\Core\Portable\Collections\ImmutableArrayExtensions.cs">
+      <Link>InternalUtilities\ImmutableArrayExtensions.cs</Link>
+    </Compile>
     <Compile Include="..\..\..\Compilers\Core\Portable\MetadataReference\MetadataFileReferenceProvider.cs">
       <Link>MetadataReference\MetadataFileReferenceProvider.cs</Link>
     </Compile>
@@ -188,9 +191,6 @@
     <Compile Include="..\..\..\Compilers\Core\Portable\InternalUtilities\WeakReferenceExtensions.cs">
       <Link>InternalUtilities\WeakReferenceExtensions.cs</Link>
     </Compile>
-    <Compile Include="..\..\..\Compilers\Core\Portable\InternalUtilities\ObjectPool`1.cs">
-      <Link>InternalUtilities\ObjectPool`1.cs</Link>
-    </Compile>
     <Compile Include="..\..\..\Compilers\Core\Portable\Serialization\FixedObjectBinder.cs">
       <Link>Serialization\FixedObjectBinder.cs</Link>
     </Compile>
@@ -953,6 +953,7 @@
       <SubType>Designer</SubType>
     </None>
   </ItemGroup>
+  <Import Project="..\..\..\Compilers\Core\SharedCollections\SharedCollections.projitems" Label="Shared" />
   <ImportGroup Label="Targets">
     <Import Project="..\..\..\Tools\Microsoft.CodeAnalysis.Toolset.Open\Targets\VSL.Imports.targets" />
     <Import Project="..\..\..\..\packages\StyleCop.MSBuild.4.7.48.2\build\StyleCop.MSBuild.Targets" Condition="Exists('..\..\..\..\packages\StyleCop.MSBuild.4.7.48.2\build\StyleCop.MSBuild.Targets')" />