diff --git a/ClosedXML/Excel/Drawings/IXLPictures.cs b/ClosedXML/Excel/Drawings/IXLPictures.cs
index ff449cd..34ed782 100644
--- a/ClosedXML/Excel/Drawings/IXLPictures.cs
+++ b/ClosedXML/Excel/Drawings/IXLPictures.cs
@@ -25,12 +25,14 @@
 
         IXLPicture Add(String imageFile, String name);
 
+        bool Contains(String pictureName);
+
         void Delete(String pictureName);
 
         void Delete(IXLPicture picture);
 
         IXLPicture Picture(String pictureName);
 
-        bool TryGetPicture(string pictureName, out IXLPicture picture);
+        bool TryGetPicture(String pictureName, out IXLPicture picture);
     }
 }
diff --git a/ClosedXML/Excel/Drawings/XLPicture.cs b/ClosedXML/Excel/Drawings/XLPicture.cs
index d0732db..e79bd12 100644
--- a/ClosedXML/Excel/Drawings/XLPicture.cs
+++ b/ClosedXML/Excel/Drawings/XLPicture.cs
@@ -14,7 +14,6 @@
     {
         private const String InvalidNameChars = @":\/?*[]";
         private static IDictionary<XLPictureFormat, ImageFormat> FormatMap;
-        private readonly IXLWorksheet _worksheet;
         private Int32 height;
         private Int32 id;
         private String name = string.Empty;
@@ -95,8 +94,7 @@
 
         private XLPicture(IXLWorksheet worksheet)
         {
-            if (worksheet == null) throw new ArgumentNullException(nameof(worksheet));
-            this._worksheet = worksheet;
+            this.Worksheet = worksheet ?? throw new ArgumentNullException(nameof(worksheet));
             this.Placement = XLPicturePlacement.MoveAndSize;
             this.Markers = new Dictionary<XLMarkerPosition, IXLMarker>()
             {
@@ -121,7 +119,7 @@
 
             private set
             {
-                if (!value.Worksheet.Equals(this._worksheet))
+                if (!value.Worksheet.Equals(this.Worksheet))
                     throw new ArgumentOutOfRangeException(nameof(value.Worksheet));
                 this.Markers[XLMarkerPosition.BottomRight] = new XLMarker(value);
             }
@@ -145,7 +143,7 @@
             get { return id; }
             internal set
             {
-                if ((_worksheet.Pictures.FirstOrDefault(p => p.Id.Equals(value)) ?? this) != this)
+                if ((Worksheet.Pictures.FirstOrDefault(p => p.Id.Equals(value)) ?? this) != this)
                     throw new ArgumentException($"The picture ID '{value}' already exists.");
 
                 id = value;
@@ -162,7 +160,7 @@
                 if (this.Placement != XLPicturePlacement.FreeFloating)
                     throw new ArgumentException("To set the left-hand offset, the placement should be FreeFloating");
 
-                Markers[XLMarkerPosition.TopLeft] = new XLMarker(_worksheet.Cell(1, 1).Address, new Point(value, this.Top));
+                Markers[XLMarkerPosition.TopLeft] = new XLMarker(Worksheet.Cell(1, 1).Address, new Point(value, this.Top));
             }
         }
 
@@ -173,7 +171,7 @@
             {
                 if (name == value) return;
 
-                if ((_worksheet.Pictures.FirstOrDefault(p => p.Name.Equals(value, StringComparison.OrdinalIgnoreCase)) ?? this) != this)
+                if ((Worksheet.Pictures.FirstOrDefault(p => p.Name.Equals(value, StringComparison.OrdinalIgnoreCase)) ?? this) != this)
                     throw new ArgumentException($"The picture name '{value}' already exists.");
 
                 SetName(value);
@@ -194,7 +192,7 @@
                 if (this.Placement != XLPicturePlacement.FreeFloating)
                     throw new ArgumentException("To set the top offset, the placement should be FreeFloating");
 
-                Markers[XLMarkerPosition.TopLeft] = new XLMarker(_worksheet.Cell(1, 1).Address, new Point(this.Left, value));
+                Markers[XLMarkerPosition.TopLeft] = new XLMarker(Worksheet.Cell(1, 1).Address, new Point(this.Left, value));
             }
         }
 
@@ -207,7 +205,7 @@
 
             private set
             {
-                if (!value.Worksheet.Equals(this._worksheet))
+                if (!value.Worksheet.Equals(this.Worksheet))
                     throw new ArgumentOutOfRangeException(nameof(value.Worksheet));
 
                 this.Markers[XLMarkerPosition.TopLeft] = new XLMarker(value);
@@ -225,10 +223,7 @@
             }
         }
 
-        public IXLWorksheet Worksheet
-        {
-            get { return _worksheet; }
-        }
+        public IXLWorksheet Worksheet { get; }
 
         internal IDictionary<XLMarkerPosition, IXLMarker> Markers { get; private set; }
 
diff --git a/ClosedXML/Excel/Drawings/XLPictures.cs b/ClosedXML/Excel/Drawings/XLPictures.cs
index 3cf1007..3b60573 100644
--- a/ClosedXML/Excel/Drawings/XLPictures.cs
+++ b/ClosedXML/Excel/Drawings/XLPictures.cs
@@ -12,7 +12,6 @@
     {
         private readonly List<XLPicture> _pictures = new List<XLPicture>();
         private readonly XLWorksheet _worksheet;
-        internal ICollection<String> Deleted { get; private set; }
 
         public XLPictures(XLWorksheet worksheet)
         {
@@ -26,6 +25,8 @@
             get { return _pictures.Count; }
         }
 
+        internal ICollection<String> Deleted { get; private set; }
+
         public IXLPicture Add(Stream stream)
         {
             var picture = new XLPicture(_worksheet, stream);
@@ -89,6 +90,11 @@
             return picture;
         }
 
+        public bool Contains(string pictureName)
+        {
+            return _pictures.Any(p => string.Equals(p.Name, pictureName, StringComparison.OrdinalIgnoreCase));
+        }
+
         public void Delete(IXLPicture picture)
         {
             Delete(picture.Name);
diff --git a/ClosedXML/Excel/IXLWorksheets.cs b/ClosedXML/Excel/IXLWorksheets.cs
index 6a64b8b..8b074ac 100644
--- a/ClosedXML/Excel/IXLWorksheets.cs
+++ b/ClosedXML/Excel/IXLWorksheets.cs
@@ -18,6 +18,8 @@
 
         void Add(DataSet dataSet);
 
+        Boolean Contains(String sheetName);
+
         void Delete(String sheetName);
 
         void Delete(Int32 position);
diff --git a/ClosedXML/Excel/PivotTables/IXLPivotTable.cs b/ClosedXML/Excel/PivotTables/IXLPivotTable.cs
index bcc4292..c3c6899 100644
--- a/ClosedXML/Excel/PivotTables/IXLPivotTable.cs
+++ b/ClosedXML/Excel/PivotTables/IXLPivotTable.cs
@@ -225,5 +225,7 @@
         IXLPivotTable SetLayout(XLPivotLayout value);
         IXLPivotTable SetInsertBlankLines(); IXLPivotTable SetInsertBlankLines(Boolean value);
 
+        IXLWorksheet Worksheet { get; }
+
     }
 }
diff --git a/ClosedXML/Excel/PivotTables/IXLPivotTables.cs b/ClosedXML/Excel/PivotTables/IXLPivotTables.cs
index bbce037..ce11a21 100644
--- a/ClosedXML/Excel/PivotTables/IXLPivotTables.cs
+++ b/ClosedXML/Excel/PivotTables/IXLPivotTables.cs
@@ -1,16 +1,20 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
-using System.Text;
 
 namespace ClosedXML.Excel
 {
-    public interface IXLPivotTables: IEnumerable<IXLPivotTable>
+    public interface IXLPivotTables : IEnumerable<IXLPivotTable>
     {
-        IXLPivotTable PivotTable(String name);
         void Add(String name, IXLPivotTable pivotTable);
+
         IXLPivotTable AddNew(String name, IXLCell target, IXLRange source);
+
+        Boolean Contains(String name);
+
         void Delete(String name);
+
         void DeleteAll();
+
+        IXLPivotTable PivotTable(String name);
     }
 }
diff --git a/ClosedXML/Excel/PivotTables/XLPivotTable.cs b/ClosedXML/Excel/PivotTables/XLPivotTable.cs
index 1d7895d..0e20ea8 100644
--- a/ClosedXML/Excel/PivotTables/XLPivotTable.cs
+++ b/ClosedXML/Excel/PivotTables/XLPivotTable.cs
@@ -8,10 +8,12 @@
     [DebuggerDisplay("{Name}")]
     internal class XLPivotTable : IXLPivotTable
     {
+        private String _name;
         public Guid Guid { get; private set; }
 
-        public XLPivotTable()
+        public XLPivotTable(IXLWorksheet worksheet)
         {
+            this.Worksheet = worksheet ?? throw new ArgumentNullException(nameof(worksheet));
             this.Guid = Guid.NewGuid();
 
             Fields = new XLPivotFields(this);
@@ -42,7 +44,41 @@
 
         public IXLPivotTable SetTheme(XLPivotTableTheme value) { Theme = value; return this; }
 
-        public String Name { get; set; }
+        public String Name
+        {
+            get { return _name; }
+            set
+            {
+                if (_name == value) return;
+
+                var oldname = _name ?? string.Empty;
+
+                if (String.IsNullOrWhiteSpace(value))
+                    throw new ArgumentException($"The table name '{value}' is invalid");
+
+                // Table names are case insensitive
+                if (!oldname.Equals(value, StringComparison.OrdinalIgnoreCase)
+                    && Worksheet.Tables.Any(t => t.Name.Equals(value, StringComparison.OrdinalIgnoreCase)))
+                    throw new ArgumentException($"This worksheet already contains a table named '{value}'");
+
+                if (value[0] != '_' && !char.IsLetter(value[0]))
+                    throw new ArgumentException($"The table name '{value}' does not begin with a letter or an underscore");
+
+                if (value.Length > 255)
+                    throw new ArgumentException("The table name is more than 255 characters");
+
+                if (new[] { 'C', 'R' }.Any(c => value.ToUpper().Equals(c.ToString())))
+                    throw new ArgumentException($"The table name '{value}' is invalid");
+
+                _name = value;
+
+                if (!String.IsNullOrWhiteSpace(oldname) && !String.Equals(oldname, _name, StringComparison.OrdinalIgnoreCase))
+                {
+                    Worksheet.PivotTables.Delete(oldname);
+                    Worksheet.PivotTables.Add(_name, this);
+                }
+            }
+        }
 
         public IXLPivotTable SetName(String value) { Name = value; return this; }
 
@@ -323,7 +359,8 @@
             AllowMultipleFilters = true;	//	Multiple Field Filters
             SortFieldsAtoZ = false;	//	Default Sort Order
             UseCustomListsForSorting = true; //	Custom List AutoSort
-
         }
+
+        public IXLWorksheet Worksheet { get; }
     }
 }
diff --git a/ClosedXML/Excel/PivotTables/XLPivotTables.cs b/ClosedXML/Excel/PivotTables/XLPivotTables.cs
index 6a71642..7bb7ac3 100644
--- a/ClosedXML/Excel/PivotTables/XLPivotTables.cs
+++ b/ClosedXML/Excel/PivotTables/XLPivotTables.cs
@@ -6,7 +6,12 @@
 {
     internal class XLPivotTables : IXLPivotTables
     {
-        private readonly Dictionary<String, XLPivotTable> _pivotTables = new Dictionary<string, XLPivotTable>();
+        private readonly Dictionary<String, XLPivotTable> _pivotTables = new Dictionary<string, XLPivotTable>(StringComparer.OrdinalIgnoreCase);
+
+        public XLPivotTables(IXLWorksheet worksheet)
+        {
+            this.Worksheet = worksheet ?? throw new ArgumentNullException(nameof(worksheet));
+        }
 
         public void Add(String name, IXLPivotTable pivotTable)
         {
@@ -15,11 +20,21 @@
 
         public IXLPivotTable AddNew(string name, IXLCell target, IXLRange source)
         {
-            var pivotTable = new XLPivotTable { Name = name, TargetCell = target, SourceRange = source };
+            var pivotTable = new XLPivotTable(this.Worksheet)
+            {
+                Name = name,
+                TargetCell = target,
+                SourceRange = source
+            };
             _pivotTables.Add(name, pivotTable);
             return pivotTable;
         }
 
+        public Boolean Contains(String name)
+        {
+            return _pivotTables.ContainsKey(name);
+        }
+
         public void Delete(String name)
         {
             _pivotTables.Remove(name);
@@ -49,5 +64,7 @@
         {
             return PivotTable(name);
         }
+
+        public IXLWorksheet Worksheet { get; private set; }
     }
 }
diff --git a/ClosedXML/Excel/Tables/IXLTables.cs b/ClosedXML/Excel/Tables/IXLTables.cs
index cf864d3..98f19dc 100644
--- a/ClosedXML/Excel/Tables/IXLTables.cs
+++ b/ClosedXML/Excel/Tables/IXLTables.cs
@@ -7,18 +7,20 @@
     {
         void Add(IXLTable table);
 
-        IXLTable Table(Int32 index);
-
-        IXLTable Table(String name);
-
         /// <summary>
         /// Clears the contents of these tables.
         /// </summary>
         /// <param name="clearOptions">Specify what you want to clear.</param>
         IXLTables Clear(XLClearOptions clearOptions = XLClearOptions.All);
 
+        Boolean Contains(String name);
+
         void Remove(Int32 index);
 
         void Remove(String name);
+
+        IXLTable Table(Int32 index);
+
+        IXLTable Table(String name);
     }
 }
diff --git a/ClosedXML/Excel/Tables/XLTable.cs b/ClosedXML/Excel/Tables/XLTable.cs
index b7a791c..b1068d7 100644
--- a/ClosedXML/Excel/Tables/XLTable.cs
+++ b/ClosedXML/Excel/Tables/XLTable.cs
@@ -234,7 +234,7 @@
                 if (_fieldNames?.Any() ?? false)
                     this.Fields.ForEach(f => (f as XLTableField).UpdateTableFieldTotalsRowFormula());
 
-                if (!String.IsNullOrWhiteSpace(oldname))
+                if (!String.IsNullOrWhiteSpace(oldname) && !String.Equals(oldname, _name, StringComparison.OrdinalIgnoreCase))
                 {
                     Worksheet.Tables.Add(this);
                     Worksheet.Tables.Remove(oldname);
diff --git a/ClosedXML/Excel/Tables/XLTables.cs b/ClosedXML/Excel/Tables/XLTables.cs
index 9ae8e7f..2773e51 100644
--- a/ClosedXML/Excel/Tables/XLTables.cs
+++ b/ClosedXML/Excel/Tables/XLTables.cs
@@ -9,16 +9,34 @@
     internal class XLTables : IXLTables
     {
         private readonly Dictionary<String, IXLTable> _tables;
-        internal ICollection<String> Deleted { get; private set; }
 
         public XLTables()
         {
-            _tables = new Dictionary<String, IXLTable>();
+            _tables = new Dictionary<String, IXLTable>(StringComparer.OrdinalIgnoreCase);
             Deleted = new HashSet<String>();
         }
 
+        internal ICollection<String> Deleted { get; private set; }
+
         #region IXLTables Members
 
+        public void Add(IXLTable table)
+        {
+            _tables.Add(table.Name, table);
+            (table as XLTable)?.OnAddedToTables();
+        }
+
+        public IXLTables Clear(XLClearOptions clearOptions = XLClearOptions.All)
+        {
+            _tables.Values.ForEach(t => t.Clear(clearOptions));
+            return this;
+        }
+
+        public Boolean Contains(String name)
+        {
+            return _tables.ContainsKey(name);
+        }
+
         public IEnumerator<IXLTable> GetEnumerator()
         {
             return _tables.Values.GetEnumerator();
@@ -29,30 +47,6 @@
             return GetEnumerator();
         }
 
-        public void Add(IXLTable table)
-        {
-            _tables.Add(table.Name, table);
-            (table as XLTable)?.OnAddedToTables();
-        }
-
-        public IXLTable Table(Int32 index)
-        {
-            return _tables.ElementAt(index).Value;
-        }
-
-        public IXLTable Table(String name)
-        {
-            return _tables[name];
-        }
-
-        #endregion IXLTables Members
-
-        public IXLTables Clear(XLClearOptions clearOptions = XLClearOptions.All)
-        {
-            _tables.Values.ForEach(t => t.Clear(clearOptions));
-            return this;
-        }
-
         public void Remove(Int32 index)
         {
             this.Remove(_tables.ElementAt(index).Key);
@@ -68,5 +62,17 @@
 
             if (table.RelId != null) Deleted.Add(table.RelId);
         }
+
+        public IXLTable Table(Int32 index)
+        {
+            return _tables.ElementAt(index).Value;
+        }
+
+        public IXLTable Table(String name)
+        {
+            return _tables[name];
+        }
+
+        #endregion IXLTables Members
     }
 }
diff --git a/ClosedXML/Excel/XLWorksheet.cs b/ClosedXML/Excel/XLWorksheet.cs
index 826f35b..a8946b3 100644
--- a/ClosedXML/Excel/XLWorksheet.cs
+++ b/ClosedXML/Excel/XLWorksheet.cs
@@ -62,7 +62,7 @@
             Tables = new XLTables();
             Hyperlinks = new XLHyperlinks();
             DataValidations = new XLDataValidations();
-            PivotTables = new XLPivotTables();
+            PivotTables = new XLPivotTables(this);
             Protection = new XLSheetProtection();
             AutoFilter = new XLAutoFilter();
             ConditionalFormats = new XLConditionalFormats();
diff --git a/ClosedXML/Excel/XLWorksheets.cs b/ClosedXML/Excel/XLWorksheets.cs
index 0fd1528..62b379a 100644
--- a/ClosedXML/Excel/XLWorksheets.cs
+++ b/ClosedXML/Excel/XLWorksheets.cs
@@ -13,7 +13,7 @@
         #region Constructor
 
         private readonly XLWorkbook _workbook;
-        private readonly Dictionary<String, XLWorksheet> _worksheets = new Dictionary<String, XLWorksheet>();
+        private readonly Dictionary<String, XLWorksheet> _worksheets = new Dictionary<String, XLWorksheet>(StringComparer.OrdinalIgnoreCase);
         internal ICollection<String> Deleted { get; private set; }
 
         #endregion Constructor
@@ -45,9 +45,14 @@
             get { return _worksheets.Count; }
         }
 
+        public Boolean Contains(String sheetName)
+        {
+            return _worksheets.ContainsKey(sheetName);
+        }
+
         public bool TryGetWorksheet(string sheetName, out IXLWorksheet worksheet)
         {
-            if (_worksheets.TryGetValue(sheetName.UnescapeSheetName().ToLowerInvariant(), out XLWorksheet w))
+            if (_worksheets.TryGetValue(sheetName.UnescapeSheetName(), out XLWorksheet w))
             {
                 worksheet = w;
                 return true;
@@ -60,12 +65,11 @@
         {
             sheetName = sheetName.UnescapeSheetName();
 
-            if (_worksheets.TryGetValue(sheetName.ToLowerInvariant(), out XLWorksheet w))
+            if (_worksheets.TryGetValue(sheetName, out XLWorksheet w))
                 return w;
 
-            var wss = _worksheets.Where(ws => string.Equals(ws.Key, sheetName, StringComparison.OrdinalIgnoreCase));
-            if (wss.Any())
-                return wss.First().Value;
+            if (_worksheets.ContainsKey(sheetName))
+                return _worksheets[sheetName];
 
             throw new ArgumentException("There isn't a worksheet named '" + sheetName + "'.");
         }
@@ -105,15 +109,15 @@
 
         private void Add(String sheetName, XLWorksheet sheet)
         {
-            if (_worksheets.Any(ws => ws.Key.Equals(sheetName, StringComparison.OrdinalIgnoreCase)))
+            if (_worksheets.ContainsKey(sheetName))
                 throw new ArgumentException(String.Format("A worksheet with the same name ({0}) has already been added.", sheetName), nameof(sheetName));
 
-            _worksheets.Add(sheetName.ToLowerInvariant(), sheet);
+            _worksheets.Add(sheetName, sheet);
         }
 
         public void Delete(String sheetName)
         {
-            Delete(_worksheets[sheetName.ToLowerInvariant()].Position);
+            Delete(_worksheets[sheetName].Position);
         }
 
         public void Delete(Int32 position)
@@ -169,14 +173,14 @@
 
         public void Rename(String oldSheetName, String newSheetName)
         {
-            if (String.IsNullOrWhiteSpace(oldSheetName) || !_worksheets.ContainsKey(oldSheetName.ToLowerInvariant())) return;
+            if (String.IsNullOrWhiteSpace(oldSheetName) || !_worksheets.ContainsKey(oldSheetName)) return;
 
             if (!oldSheetName.Equals(newSheetName, StringComparison.OrdinalIgnoreCase)
-                && _worksheets.Any(ws1 => ws1.Key.Equals(newSheetName, StringComparison.OrdinalIgnoreCase)))
+                && _worksheets.ContainsKey(newSheetName))
                 throw new ArgumentException(String.Format("A worksheet with the same name ({0}) has already been added.", newSheetName), nameof(newSheetName));
 
-            var ws = _worksheets[oldSheetName.ToLowerInvariant()];
-            _worksheets.Remove(oldSheetName.ToLowerInvariant());
+            var ws = _worksheets[oldSheetName];
+            _worksheets.Remove(oldSheetName);
             Add(newSheetName, ws);
         }
     }