diff --git a/ClosedXML/ClosedXML/ClosedXML.sln b/ClosedXML/ClosedXML/ClosedXML.sln
index 3c43b32..6f03ef0 100644
--- a/ClosedXML/ClosedXML/ClosedXML.sln
+++ b/ClosedXML/ClosedXML/ClosedXML.sln
@@ -1,6 +1,8 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio 2010
+# Visual Studio 2013
+VisualStudioVersion = 12.0.21005.1
+MinimumVisualStudioVersion = 10.0.40219.1
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ClosedXML_Sandbox", "ClosedXML_Sandbox\ClosedXML_Sandbox.csproj", "{38B882F0-E6F2-45C5-9BE9-CDC27FBEB4AB}"
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{5C94E22C-85AA-48FD-B082-CF929FFC6C31}"
@@ -30,9 +32,6 @@
 	EndProjectSection
 EndProject
 Global
-	GlobalSection(TestCaseManagementSettings) = postSolution
-		CategoryFile = ClosedXML.vsmdi
-	EndGlobalSection
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
 		Debug|Mixed Platforms = Debug|Mixed Platforms
@@ -54,8 +53,8 @@
 		{38B882F0-E6F2-45C5-9BE9-CDC27FBEB4AB}.Debug|x86.Build.0 = Debug|x86
 		{38B882F0-E6F2-45C5-9BE9-CDC27FBEB4AB}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{38B882F0-E6F2-45C5-9BE9-CDC27FBEB4AB}.Release|Any CPU.Build.0 = Release|Any CPU
-		{38B882F0-E6F2-45C5-9BE9-CDC27FBEB4AB}.Release|Mixed Platforms.ActiveCfg = Release|Any CPU
-		{38B882F0-E6F2-45C5-9BE9-CDC27FBEB4AB}.Release|Mixed Platforms.Build.0 = Release|Any CPU
+		{38B882F0-E6F2-45C5-9BE9-CDC27FBEB4AB}.Release|Mixed Platforms.ActiveCfg = Release|x64
+		{38B882F0-E6F2-45C5-9BE9-CDC27FBEB4AB}.Release|Mixed Platforms.Build.0 = Release|x64
 		{38B882F0-E6F2-45C5-9BE9-CDC27FBEB4AB}.Release|x64.ActiveCfg = Release|x64
 		{38B882F0-E6F2-45C5-9BE9-CDC27FBEB4AB}.Release|x64.Build.0 = Release|x64
 		{38B882F0-E6F2-45C5-9BE9-CDC27FBEB4AB}.Release|x86.ActiveCfg = Release|Any CPU
@@ -102,8 +101,8 @@
 		{BD5E6BFE-E837-4A35-BCA9-39667D873A20}.Debug|x86.Build.0 = Debug|x86
 		{BD5E6BFE-E837-4A35-BCA9-39667D873A20}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{BD5E6BFE-E837-4A35-BCA9-39667D873A20}.Release|Any CPU.Build.0 = Release|Any CPU
-		{BD5E6BFE-E837-4A35-BCA9-39667D873A20}.Release|Mixed Platforms.ActiveCfg = Release|Any CPU
-		{BD5E6BFE-E837-4A35-BCA9-39667D873A20}.Release|Mixed Platforms.Build.0 = Release|Any CPU
+		{BD5E6BFE-E837-4A35-BCA9-39667D873A20}.Release|Mixed Platforms.ActiveCfg = Release|x64
+		{BD5E6BFE-E837-4A35-BCA9-39667D873A20}.Release|Mixed Platforms.Build.0 = Release|x64
 		{BD5E6BFE-E837-4A35-BCA9-39667D873A20}.Release|x64.ActiveCfg = Release|x64
 		{BD5E6BFE-E837-4A35-BCA9-39667D873A20}.Release|x64.Build.0 = Release|x64
 		{BD5E6BFE-E837-4A35-BCA9-39667D873A20}.Release|x86.ActiveCfg = Release|Any CPU
@@ -136,4 +135,10 @@
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
 	EndGlobalSection
+	GlobalSection(Performance) = preSolution
+		HasPerformanceSessions = true
+	EndGlobalSection
+	GlobalSection(TestCaseManagementSettings) = postSolution
+		CategoryFile = ClosedXML.vsmdi
+	EndGlobalSection
 EndGlobal
diff --git a/ClosedXML/ClosedXML/ClosedXML/Excel/Cells/XLCell.cs b/ClosedXML/ClosedXML/ClosedXML/Excel/Cells/XLCell.cs
index 08fa698..20cd3d3 100644
--- a/ClosedXML/ClosedXML/ClosedXML/Excel/Cells/XLCell.cs
+++ b/ClosedXML/ClosedXML/ClosedXML/Excel/Cells/XLCell.cs
@@ -22,7 +22,7 @@
         private static readonly Regex A1Regex = new Regex(
             @"(?<=\W)(\$?[a-zA-Z]{1,3}\$?\d{1,7})(?=\W)" // A1
             + @"|(?<=\W)(\$?\d{1,7}:\$?\d{1,7})(?=\W)" // 1:1
-            + @"|(?<=\W)(\$?[a-zA-Z]{1,3}:\$?[a-zA-Z]{1,3})(?=\W)"); // A:A
+            + @"|(?<=\W)(\$?[a-zA-Z]{1,3}:\$?[a-zA-Z]{1,3})(?=\W)", RegexOptions.Compiled); // A:A
 
         public static readonly Regex A1SimpleRegex = new Regex(
             //  @"(?<=\W)" // Start with non word
@@ -45,22 +45,22 @@
             + @")" // End Range
             + @")" // End Group to pick
             //+ @"(?=\W)" // End with non word
-            );
+            , RegexOptions.Compiled);
 
         private static readonly Regex A1RowRegex = new Regex(
             @"(\$?\d{1,7}:\$?\d{1,7})" // 1:1
-            );
+            , RegexOptions.Compiled);
 
         private static readonly Regex A1ColumnRegex = new Regex(
             @"(\$?[a-zA-Z]{1,3}:\$?[a-zA-Z]{1,3})" // A:A
-            );
+            , RegexOptions.Compiled);
 
         private static readonly Regex R1C1Regex = new Regex(
             @"(?<=\W)([Rr]\[?-?\d{0,7}\]?[Cc]\[?-?\d{0,7}\]?)(?=\W)" // R1C1
             + @"|(?<=\W)([Rr]\[?-?\d{0,7}\]?:[Rr]\[?-?\d{0,7}\]?)(?=\W)" // R:R
-            + @"|(?<=\W)([Cc]\[?-?\d{0,5}\]?:[Cc]\[?-?\d{0,5}\]?)(?=\W)"); // C:C
+            + @"|(?<=\W)([Cc]\[?-?\d{0,5}\]?:[Cc]\[?-?\d{0,5}\]?)(?=\W)", RegexOptions.Compiled); // C:C
 
-        private static readonly Regex utfPattern = new Regex(@"(?<!_x005F)_x(?!005F)([0-9A-F]{4})_");
+        private static readonly Regex utfPattern = new Regex(@"(?<!_x005F)_x(?!005F)([0-9A-F]{4})_", RegexOptions.Compiled);
 
         #region Fields
 
diff --git a/ClosedXML/ClosedXML/ClosedXML/Excel/Coordinates/XLSheetPoint.cs b/ClosedXML/ClosedXML/ClosedXML/Excel/Coordinates/XLSheetPoint.cs
index e1beef7..1d71682 100644
--- a/ClosedXML/ClosedXML/ClosedXML/Excel/Coordinates/XLSheetPoint.cs
+++ b/ClosedXML/ClosedXML/ClosedXML/Excel/Coordinates/XLSheetPoint.cs
@@ -13,6 +13,11 @@
         public readonly Int32 Row;
         public readonly Int32 Column;
 
+        public override bool Equals(object obj)
+        {
+            return Equals((XLSheetPoint)obj);
+        }
+
         public bool Equals(XLSheetPoint other)
         {
             return Row == other.Row && Column == other.Column;
@@ -22,5 +27,15 @@
         {
             return (Row * -1) ^ Column;
         }
+
+        public static bool operator==(XLSheetPoint a, XLSheetPoint b)
+        {
+            return a.Row == b.Row && a.Column == b.Column;
+        }
+
+        public static bool operator !=(XLSheetPoint a, XLSheetPoint b)
+        {
+            return a.Row != b.Row || a.Column != b.Column;
+        }
     }
 }
diff --git a/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Save.cs b/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Save.cs
index d8a25cb..0b7840d 100644
--- a/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Save.cs
+++ b/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Save.cs
@@ -4052,7 +4052,9 @@
                         cell = cellsByReference[cellReference];
                     else
                     {
-                        cell = new Cell {CellReference = new StringValue(cellReference)};
+                        cell = new Cell();
+                        cell.CellReference = new StringValue(cellReference);
+                        
                         if (isNewRow)
                             row.AppendChild(cell);
                         else
diff --git a/ClosedXML/ClosedXML/ClosedXML/Extensions.cs b/ClosedXML/ClosedXML/ClosedXML/Extensions.cs
index a609022..876a2af 100644
--- a/ClosedXML/ClosedXML/ClosedXML/Extensions.cs
+++ b/ClosedXML/ClosedXML/ClosedXML/Extensions.cs
@@ -103,7 +103,7 @@
 
     public static class StringExtensions
     {
-        private static readonly Regex RegexNewLine = new Regex(@"((?<!\r)\n|\r\n)");
+        private static readonly Regex RegexNewLine = new Regex(@"((?<!\r)\n|\r\n)", RegexOptions.Compiled);
         public static String FixNewLines(this String value)
         {
             return value.Contains("\n") ? RegexNewLine.Replace(value, Environment.NewLine) : value;
diff --git a/ClosedXML/ClosedXML/ClosedXML/XLHelper.cs b/ClosedXML/ClosedXML/ClosedXML/XLHelper.cs
index e40da42..6bb853c 100644
--- a/ClosedXML/ClosedXML/ClosedXML/XLHelper.cs
+++ b/ClosedXML/ClosedXML/ClosedXML/XLHelper.cs
@@ -47,55 +47,78 @@
             + @")" // End Range
             + @")" // End Group to pick
             + @"\Z"
-            );
+            , RegexOptions.Compiled);
 
         internal static readonly Regex NamedRangeReferenceRegex =
             new Regex(@"^('?(?<Sheet>[^'!]+)'?!(?<Range>.+))|((?<Table>[^\[]+)\[(?<Column>[^\]]+)\])$",
                       RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.ExplicitCapture
                 );
 
+        private static Dictionary<string, int> columnNumbers = new Dictionary<string, int>();
         /// <summary>
         /// 	Gets the column number of a given column letter.
         /// </summary>
         /// <param name="columnLetter"> The column letter to translate into a column number. </param>
         public static int GetColumnNumberFromLetter(string columnLetter)
         {
-            if (columnLetter[0] <= '9')
-                return Int32.Parse(columnLetter, NumberFormatForParse);
-
+            int retVal;
             columnLetter = columnLetter.ToUpper();
+            if (columnNumbers.TryGetValue(columnLetter, out retVal))
+                return retVal;
+
+            if (columnLetter[0] <= '9')
+            {
+                retVal = Int32.Parse(columnLetter, NumberFormatForParse);
+                columnNumbers.Add(columnLetter, retVal);
+                return retVal;
+            }
+            
             var length = columnLetter.Length;
             if (length == 1)
-                return Convert.ToByte(columnLetter[0]) - 64;
+            {
+                retVal = Convert.ToByte(columnLetter[0]) - 64;
+                columnNumbers.Add(columnLetter, retVal);
+                return retVal;
+            }
             if (length == 2)
             {
-                return
+                retVal =
                     ((Convert.ToByte(columnLetter[0]) - 64)*26) +
                     (Convert.ToByte(columnLetter[1]) - 64);
+                columnNumbers.Add(columnLetter, retVal);
+                return retVal;
             }
             if (length == 3)
             {
-                return ((Convert.ToByte(columnLetter[0]) - 64)*TwoT26) +
+                retVal = ((Convert.ToByte(columnLetter[0]) - 64)*TwoT26) +
                        ((Convert.ToByte(columnLetter[1]) - 64)*26) +
                        (Convert.ToByte(columnLetter[2]) - 64);
+                columnNumbers.Add(columnLetter, retVal);
+                return retVal;
             }
             throw new ApplicationException("Column Length must be between 1 and 3.");
         }
 
+        private static Dictionary<int, string> columnLetters = new Dictionary<int, string>();
         /// <summary>
         /// 	Gets the column letter of a given column number.
         /// </summary>
         /// <param name="column"> The column number to translate into a column letter. </param>
-        public static string GetColumnLetterFromNumber(int column)
+        public static string GetColumnLetterFromNumber(int columnNumber)
         {
+            String retVal;
+            if (columnLetters.TryGetValue(columnNumber, out retVal))
+                return retVal;
+
             #region Check
 
-            if (column <= 0)
+            if (columnNumber <= 0)
                 throw new ArgumentOutOfRangeException("column", "Must be more than 0");
 
             #endregion
 
             var value = new StringBuilder(6);
+            int column = columnNumber;
             while (column > 0)
             {
                 var residue = column%26;
@@ -107,7 +130,9 @@
                 }
                 value.Insert(0, (char) (64 + residue));
             }
-            return value.ToString();
+            retVal = value.ToString();
+            columnLetters.Add(columnNumber, retVal);
+            return retVal;
         }
 
         public static bool IsValidColumn(string column)
diff --git a/ClosedXML/ClosedXML/ClosedXML_Sandbox/Program.cs b/ClosedXML/ClosedXML/ClosedXML_Sandbox/Program.cs
index 40bf205..5145c4d 100644
--- a/ClosedXML/ClosedXML/ClosedXML_Sandbox/Program.cs
+++ b/ClosedXML/ClosedXML/ClosedXML_Sandbox/Program.cs
@@ -6,10 +6,13 @@
 using ClosedXML;
 using System.Drawing;
 using System.IO;
+using DocumentFormat.OpenXml.Spreadsheet;
+using DocumentFormat.OpenXml;
 namespace ClosedXML_Sandbox
 {
     class Program
     {
+
         static void Main(string[] args)
         {
             var wb = new XLWorkbook();
@@ -19,7 +22,7 @@
             foreach (var sheetId in Enumerable.Range(1, 4))
             {
                 var ws = wb.AddWorksheet("Sheet" + sheetId);
-                foreach (var ro in Enumerable.Range(1, 40000))
+                foreach (var ro in Enumerable.Range(1, 4000))
                 {
                     foreach (var co in Enumerable.Range(1, 30))
                     {
@@ -28,13 +31,13 @@
                 }
             }
             var end = DateTime.Now;
-            Console.WriteLine((end - start).TotalMinutes);
+            Console.WriteLine((end - start).TotalSeconds);
 
             Console.WriteLine("Saving");
             start = DateTime.Now;
             wb.SaveAs(@"c:\temp\saved.xlsx");
             end = DateTime.Now;
-            Console.WriteLine((end - start).TotalMinutes);
+            Console.WriteLine((end - start).TotalSeconds);
 
             Console.WriteLine("Done");
             Console.ReadKey();