@@ -41,7 +41,6 @@ local coroutine = coroutine
 local ccreate = coroutine.create
 local cresume = coroutine.resume
 local cyield = coroutine.yield
-local pairs = pairs
 
 local Collection = {}
 local null = {}
@@ -532,7 +531,7 @@ local function ipairsArray(t)
   end, t, 1
 end
 
-local pairsFn = pairs(null)
+local pairsFn = next
 
 local function pairsDict(t)
   local version = versions[t]
@@ -647,8 +646,10 @@ function Collection.toArray(t)
   if isArrayLike(t) then
     tmove(t, 1, #t, 1, array)
   else
+    local count = 1
     for _, v in each(t) do
-      array[#array + 1] = wrap(v)
+      array[count] = wrap(v)
+      count = count + 1
     end
   end
   return System.arrayFromTable(array, t.__genericT__)
@@ -714,7 +715,7 @@ function DictionaryEnumerator.MoveNext(this)
       pair.Value = unWrap(v)
       this.current = pair
     elseif this.kind == 1 then
-      this.current = unWrap(k)
+      this.current = k
     else
       this.current = unWrap(v)
     end
 
@@ -625,8 +625,7 @@ local function toString(value, startIndex, length)
     t[len + 2] = 45
     len = len + 3
   end
-  t[len - 1] = nil
-  return schar(unpack(t))
+  return schar(unpack(t, 1, len - 1))
 end
 
 local function doubleToInt64Bits(value)
 
@@ -81,16 +81,15 @@ local function equalsMulticast(fn1, fn2, start, count)
 end
 
 local function delete(fn, count, deleteIndex, deleteCount)
-  local t = {}
-  local count = 1
-  setmetatable(t, multicast)
+  local t =  setmetatable({}, multicast)
+  local len = 1
   for i = 1, deleteIndex - 1 do
-    t[count] = fn[i]
-    count = count + 1
+    t[len] = fn[i]
+    len = len + 1
   end
   for i = deleteIndex + deleteCount, count do
-    t[count] = fn[i]
-    count = count + 1
+    t[len] = fn[i]
+    len = len + 1
   end
   return t
 end
 
@@ -120,8 +120,10 @@ function StringBuilder.AppendCharRepeat(this, v, repeatCount)
   if repeatCount < 0 then throw(ArgumentOutOfRangeException("repeatCount")) end
   if repeatCount == 0 then return this end
   v = schar(v)
+  local count = #this + 1
   for i = 1, repeatCount do
-    this[#this + 1] = v
+    this[count] = v
+    count = count + 1
   end
   addCount(this, repeatCount) 
   return this
@@ -135,12 +137,14 @@ function StringBuilder.AppendFormat(this, format, ...)
 end
 
 function StringBuilder.AppendLine(this, value)
-  local count = 1;
+  local count = 1
+  local len = #this + 1
   if value ~= nil then
-    this[#this + 1] = value
+    this[len] = value
+    len = len + 1
     count = count + #value
   end
-  this[#this + 1] = "\n"
+  this[len] = "\n"
   addCount(this, count) 
   return this
 end
 
@@ -249,21 +249,22 @@ define("System.Guid", {
       local b = ...
       if b == nil then throw(ArgumentNullException()) end
       if type(b) ~= "string" then
-        local i = sl(b:get(3), 24)
-        i = bor(i, sl(b:get(2), 16))
-        i = bor(i, sl(b:get(1), 8))
-        i = bor(i, b:get(0))
+        local get = b.get
+        local i = sl(get(b, 3), 24)
+        i = bor(i, sl(get(b, 2), 16))
+        i = bor(i, sl(get(b, 1), 8))
+        i = bor(i, get(b, 0))
         this.a = i
-        this.b = bor(sl(b:get(5), 8), b:get(4))
-        this.c = bor(sl(b:get(7), 8), b:get(6))
-        this.d = b:get(8)
-        this.e = b:get(9)
-        this.f = b:get(10)
-        this.g = b:get(11)
-        this.h = b:get(12)
-        this.i = b:get(13)
-        this.j = b:get(14)
-        this.k = b:get(15)
+        this.b = bor(sl(get(b, 5), 8), get(b, 4))
+        this.c = bor(sl(get(b, 7), 8), get(b, 6))
+        this.d = get(b, 8)
+        this.e = get(b, 9)
+        this.f = get(b, 10)
+        this.g = get(b, 11)
+        this.h = get(b, 12)
+        this.i = get(b, 13)
+        this.j = get(b, 14)
+        this.k = get(b, 15)
       else
         assert(false)
       end