diff --git a/CSharp.lua/CoreSystem.Lua/CoreSystem/Array.lua b/CSharp.lua/CoreSystem.Lua/CoreSystem/Array.lua
index 2064ca80..ccd7ae2f 100644
--- a/CSharp.lua/CoreSystem.Lua/CoreSystem/Array.lua
+++ b/CSharp.lua/CoreSystem.Lua/CoreSystem/Array.lua
@@ -59,7 +59,7 @@ if coroutine ~= nil then
   cyield = coroutine.yield
 end
 
-local null = {}
+local null = { GetHashCode = System.zeroFn }
 local arrayEnumerator
 local arrayFromTable
 
@@ -527,9 +527,8 @@ end
 local function checkOrderUniqueAndUnfoundElements(t, n, comparer, other, returnIfUnfound)
   if n == 0 then
     local numElementsInOther = 0
-    for _, v in each(other) do
-      numElementsInOther = numElementsInOther + 1
-      break
+    if other:GetEnumerator():MoveNext() then
+      numElementsInOther = 1
     end
     return 0, numElementsInOther
   end
diff --git a/CSharp.lua/CoreSystem.Lua/CoreSystem/Collections/Linq.lua b/CSharp.lua/CoreSystem.Lua/CoreSystem/Collections/Linq.lua
index 3c214ff9..a710d526 100644
--- a/CSharp.lua/CoreSystem.Lua/CoreSystem/Collections/Linq.lua
+++ b/CSharp.lua/CoreSystem.Lua/CoreSystem/Collections/Linq.lua
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 --]]
 
-local System = System
+local System = _G.System
 local define = System.define
 local throw = System.throw
 local each = System.each
@@ -38,18 +38,15 @@ local Comparer_1 = System.Comparer_1
 local Empty = System.Array.Empty
 
 local IEnumerable_1 = System.IEnumerable_1
-local IEnumerable = System.IEnumerable
 local IEnumerator_1 = System.IEnumerator_1
-local IEnumerator = System.IEnumerator
 
 local assert = assert
-local getmetatable = getmetatable
 local setmetatable = setmetatable
 local select = select
 local pairs = pairs
 local tsort = table.sort
 
-local InternalEnumerable = define("System.Linq.InternalEnumerable", function(T) 
+local InternalEnumerable = define("System.Linq.InternalEnumerable", function(T)
   return {
     base = { IEnumerable_1(T) }
   }
@@ -60,7 +57,7 @@ local function createEnumerable(T, GetEnumerator)
   return setmetatable({ __genericT__ = T, GetEnumerator = GetEnumerator }, InternalEnumerable(T))
 end
 
-local InternalEnumerator = define("System.Linq.InternalEnumerator", function(T) 
+local InternalEnumerator = define("System.Linq.InternalEnumerator", function(T)
   return {
     base = { IEnumerator_1(T) }
   }
@@ -76,10 +73,10 @@ local function createEnumerator(T, source, tryGetNext, init)
       if state == 1 then
         state = 2
         if source then
-          en = source:GetEnumerator() 
+          en = source:GetEnumerator()
         end
         if init then
-          init(en) 
+          init(en)
         end
       end
       if state == 2 then
@@ -91,7 +88,7 @@ local function createEnumerator(T, source, tryGetNext, init)
           local dispose = en.Dispose
           if dispose then
             dispose(en)
-          end    
+          end
         end
        end
        return false
@@ -109,7 +106,7 @@ function Enumerable.Where(source, predicate)
   if source == nil then throw(ArgumentNullException("source")) end
   if predicate == nil then throw(ArgumentNullException("predicate")) end
   local T = source.__genericT__
-  return createEnumerable(T, function() 
+  return createEnumerable(T, function()
     local index = -1
     return createEnumerator(T, source, function(en)
       while en:MoveNext() do
@@ -118,7 +115,7 @@ function Enumerable.Where(source, predicate)
         if predicate(current, index) then
           return true, current
         end
-      end 
+      end
       return false
     end)
   end)
@@ -129,7 +126,7 @@ function Enumerable.Select(source, selector, T)
   if selector == nil then throw(ArgumentNullException("selector")) end
   return createEnumerable(T, function()
     local index = -1
-    return createEnumerator(T, source, function(en) 
+    return createEnumerator(T, source, function(en)
       if en:MoveNext() then
         index = index + 1
         return true, selector(en:getCurrent(), index)
@@ -165,7 +162,7 @@ local function selectMany(source, collectionSelector, resultSelector, T)
   end)
 end
 
-local function identityFnOfSelectMany(s, x)
+local function identityFnOfSelectMany(_, x)
   return x
 end
 
@@ -295,9 +292,13 @@ local function getGrouping(this, key, create)
   return nil
 end
 
+local function getComparer(source, comparer)
+  return comparer or EqualityComparer(source.__genericT__).getDefault()
+end
+
 local Lookup = {
   __ctor__ = function (this, comparer)
-    this.comparer = comparer or EqualityComparer(this.__genericTKey__).getDefault()
+    this.comparer = getComparer(this, comparer)
   end,
   get = function (this, key)
     local grouping = getGrouping(this, key)
@@ -604,7 +605,7 @@ function Enumerable.Concat(first, second)
   end)
 end
 
-function Enumerable.Zip(first, second, resultSelector, TResult) 
+function Enumerable.Zip(first, second, resultSelector, TResult)
   if first == nil then throw(ArgumentNullException("first")) end
   if second == nil then throw(ArgumentNullException("second")) end
   if resultSelector == nil then throw(ArgumentNullException("resultSelector")) end
@@ -621,39 +622,15 @@ function Enumerable.Zip(first, second, resultSelector, TResult)
   end)
 end
 
-local function addToSet(set, v, getHashCode, comparer)
-  local hashCode = getHashCode(comparer, v)
-  if set[hashCode] == nil then
-    set[hashCode] = true
-    return true
-  end
-  return false
-end
-
-local function removeFromSet(set, v, getHashCode, comparer)
-  local hashCode = getHashCode(comparer, v)
-  if set[hashCode] ~= nil then
-    set[hashCode] = nil
-    return true
-  end
-  return false
-end
-
-local function getComparer(source, comparer)
-  return comparer or EqualityComparer(source.__genericT__).getDefault()
-end
-
 function Enumerable.Distinct(source, comparer)
   if source == nil then throw(ArgumentNullException("source")) end
   local T = source.__genericT__
   return createEnumerable(T, function()
-    local set = {}
-    comparer = getComparer(source, comparer)
-    local getHashCode = comparer.GetHashCodeOf
+    local set = System.HashSet(T)(comparer)
     return createEnumerator(T, source, function(en)
       while en:MoveNext() do
         local current = en:getCurrent()
-        if addToSet(set, current, getHashCode, comparer) then
+        if set:Add(current) then
           return true, current
         end
       end
@@ -667,15 +644,13 @@ function Enumerable.Union(first, second, comparer)
   if second == nil then throw(ArgumentNullException("second")) end
   local T = first.__genericT__
   return createEnumerable(T, function()
-    local set = {}
-    comparer = getComparer(first, comparer)
-    local getHashCode = comparer.GetHashCodeOf
+    local set = System.HashSet(T)(comparer)
     local secondEn
     return createEnumerator(T, first, function(en)
       if secondEn == nil then
         while en:MoveNext() do
           local current = en:getCurrent()
-          if addToSet(set, current, getHashCode, comparer) then
+          if set:Add(current) then
             return true, current
           end
         end
@@ -683,7 +658,7 @@ function Enumerable.Union(first, second, comparer)
       end
       while secondEn:MoveNext() do
         local current = secondEn:getCurrent()
-        if addToSet(set, current, getHashCode, comparer) then
+        if set:Add(current) then
           return true, current
         end
       end
@@ -697,13 +672,11 @@ function Enumerable.Intersect(first, second, comparer)
   if second == nil then throw(ArgumentNullException("second")) end
   local T = first.__genericT__
   return createEnumerable(T, function()
-    local set = {}
-    comparer = getComparer(first, comparer)
-    local getHashCode = comparer.GetHashCodeOf
+    local set = System.HashSet(T)(comparer)
     return createEnumerator(T, first, function(en)
       while en:MoveNext() do
         local current = en:getCurrent()
-        if removeFromSet(set, current, getHashCode, comparer) then
+        if set:Remove(current) then
           return true, current
         end
       end
@@ -711,10 +684,10 @@ function Enumerable.Intersect(first, second, comparer)
     end,
     function()
       for _, v in each(second) do
-        addToSet(set, v, getHashCode, comparer)
+        set:Add(v)
       end
     end)
-  end) 
+  end)
 end
 
 function Enumerable.Except(first, second, comparer)
@@ -722,13 +695,11 @@ function Enumerable.Except(first, second, comparer)
   if second == nil then throw(ArgumentNullException("second")) end
   local T = first.__genericT__
   return createEnumerable(T, function()
-    local set = {}
-    comparer = getComparer(first, comparer)
-    local getHashCode = comparer.GetHashCodeOf
+    local set = System.HashSet(T)(comparer)
     return createEnumerator(T, first, function(en)
       while en:MoveNext() do
         local current = en:getCurrent()
-        if addToSet(set, current, getHashCode, comparer) then
+        if set:Add(current) then
           return true, current
         end
       end
@@ -736,7 +707,7 @@ function Enumerable.Except(first, second, comparer)
     end,
     function()
       for _, v in each(second) do
-        addToSet(set, v, getHashCode, comparer)
+        set:Add(v)
       end
     end)
   end)
@@ -843,7 +814,7 @@ end
 function Enumerable.DefaultIfEmpty(source)
   if source == nil then throw(ArgumentNullException("source")) end
   local T = source.__genericT__
-  local state 
+  local state
   return createEnumerable(T, function()
     return createEnumerator(T, source, function(en)
       if not state then
@@ -866,7 +837,7 @@ end
 function Enumerable.OfType(source, T)
   if source == nil then throw(ArgumentNullException("source")) end
   return createEnumerable(T, function()
-    return createEnumerator(T, source, function(en) 
+    return createEnumerator(T, source, function(en)
       while en:MoveNext() do
         local current = en:getCurrent()
         if is(current, T) then
@@ -882,7 +853,7 @@ function Enumerable.Cast(source, T)
   if source == nil then throw(ArgumentNullException("source")) end
   if is(source, IEnumerable_1(T)) then return source end
   return createEnumerable(T, function()
-    return createEnumerator(T, source, function(en) 
+    return createEnumerator(T, source, function(en)
       if en:MoveNext() then
         return true, cast(T, en:getCurrent())
       end
@@ -907,7 +878,7 @@ local function first(source, ...)
       end
     else
       local en = source:GetEnumerator()
-      if en:MoveNext() then 
+      if en:MoveNext() then
         return true, en:getCurrent()
       end
     end
@@ -916,7 +887,7 @@ local function first(source, ...)
     local predicate = ...
     if predicate == nil then throw(ArgumentNullException("predicate")) end
     for _, v in each(source) do
-      if predicate(v) then 
+      if predicate(v) then
         return true, v
       end
     end
@@ -949,7 +920,7 @@ local function last(source, ...)
       end
     else
       local en = source:GetEnumerator()
-      if en:MoveNext() then 
+      if en:MoveNext() then
         local result
         repeat
           result = en:getCurrent()
@@ -967,7 +938,7 @@ local function last(source, ...)
         result = v
         found = true
       end
-    end    
+    end
     if found then return true, result end
     return false, 1
   end
@@ -1020,8 +991,8 @@ local function single(source, ...)
         found = true
       end
     end
-    if found then return true, result end    
-    return false, 0    
+    if found then return true, result end
+    return false, 0
   end
 end
 
@@ -1077,7 +1048,7 @@ function Enumerable.Range(start, count)
     return createEnumerator(Int32, nil, function()
       index = index + 1
       if index < count then
-        return true, start + index  
+        return true, start + index
       end
       return false
     end)
@@ -1091,7 +1062,7 @@ function Enumerable.Repeat(element, count, T)
     return createEnumerator(T, nil, function()
       index = index + 1
       if index < count then
-        return true, element  
+        return true, element
       end
       return false
     end)
@@ -1136,8 +1107,8 @@ function Enumerable.Count(source, ...)
     end
     local count = 0
     local en = source:GetEnumerator()
-    while en:MoveNext() do 
-      count = count + 1 
+    while en:MoveNext() do
+      count = count + 1
     end
     return count
   else
@@ -1221,7 +1192,7 @@ end
 local function minOrMax(compareFn, source, ...)
   if source == nil then throw(ArgumentNullException("source")) end
   local len = select("#", ...)
-  local selector, T 
+  local selector, T
   if len == 0 then
     selector, T = identityFn, source.__genericT__
   else
@@ -1236,7 +1207,7 @@ local function minOrMax(compareFn, source, ...)
       x = selector(x)
       if x ~= nil and (value == nil or compareFn(compare, comparer, x, value)) then
         value = x
-      end 
+      end
     end
     return value
   else
diff --git a/CSharp.lua/CoreSystem.Lua/CoreSystem/Core.lua b/CSharp.lua/CoreSystem.Lua/CoreSystem/Core.lua
index 2ae6de41..11d6d5d3 100644
--- a/CSharp.lua/CoreSystem.Lua/CoreSystem/Core.lua
+++ b/CSharp.lua/CoreSystem.Lua/CoreSystem/Core.lua
@@ -79,8 +79,8 @@ local function xpcallErr(e)
   return e
 end
 
-local function try(try, catch, finally)
-  local ok, status, result = xpcall(try, xpcallErr)
+local function try(tryFn, catch, finally)
+  local ok, status, result = xpcall(tryFn, xpcallErr)
   if not ok then
     if catch then
       if finally then
diff --git a/CSharp.lua/CoreSystem.Lua/CoreSystem/Exception.lua b/CSharp.lua/CoreSystem.Lua/CoreSystem/Exception.lua
index 3af2fb61..83dd7f9a 100644
--- a/CSharp.lua/CoreSystem.Lua/CoreSystem/Exception.lua
+++ b/CSharp.lua/CoreSystem.Lua/CoreSystem/Exception.lua
@@ -14,10 +14,10 @@ See the License for the specific language governing permissions and
 limitations under the License.
 --]]
 
-local System = System
+local System = _G.System
 local define = System.define
 local Object = System.Object
-local toString = System.toString
+local toStr = System.toString
 
 local tconcat = table.concat
 local type = type
@@ -48,11 +48,11 @@ local function getResource(t, k)
     if n == 0 then
       f = function () return s end
     elseif n == 1 then
-      f = function (x1) return s:format(toString(x1)) end
+      f = function (x1) return s:format(toStr(x1)) end
     elseif n == 2 then
-      f = function (x1, x2) return s:format(toString(x1), toString(x2)) end
+      f = function (x1, x2) return s:format(toStr(x1), toStr(x2)) end
     elseif n == 3 then
-      f = function (x1, x2, x3) return s:format(toString(x1), toString(x2), toString(x3)) end
+      f = function (x1, x2, x3) return s:format(toStr(x1), toStr(x2), toStr(x3)) end
     else
       assert(false)
     end
@@ -95,10 +95,10 @@ local Exception = define("System.Exception", {
   __ctor__ = ctorOfException,
   ToString = toString,
   getMessage = getMessage,
-  getInnerException = function(this) 
+  getInnerException = function(this)
     return this.innerException
   end,
-  getStackTrace = function(this) 
+  getStackTrace = function(this)
     return this.errorStack
   end,
   getData = function (this)
@@ -135,7 +135,7 @@ local ArgumentException = define("System.ArgumentException", {
       this.message = this.message .. " " .. resource.Arg_ParamName_Name:format(paramName)
     end
   end,
-  getParamName = function(this) 
+  getParamName = function(this)
     return this.paramName
   end
 })