diff --git a/ClosedXML/ClosedXML.csproj b/ClosedXML/ClosedXML.csproj
index 2d8b034..238169d 100644
--- a/ClosedXML/ClosedXML.csproj
+++ b/ClosedXML/ClosedXML.csproj
@@ -99,6 +99,7 @@
     <Compile Include="Excel\Style\XLPredefinedFormat.cs" />
     <Compile Include="Excel\Tables\XLTableTheme.cs" />
     <Compile Include="Excel\XLConstants.cs" />
+    <Compile Include="Excel\IXLWorkbook.cs" />
     <Compile Include="Excel\XLWorkbook_ImageHandling.cs" />
     <Compile Include="Extensions\GuidExtensions.cs" />
     <Compile Include="Extensions\OpenXmlPartContainerExtensions.cs" />
diff --git a/ClosedXML/Excel/IXLWorkbook.cs b/ClosedXML/Excel/IXLWorkbook.cs
new file mode 100644
index 0000000..702c490
--- /dev/null
+++ b/ClosedXML/Excel/IXLWorkbook.cs
@@ -0,0 +1,230 @@
+using System;
+using System.Collections.Generic;
+using System.Data;
+using System.Globalization;
+using System.IO;
+
+namespace ClosedXML.Excel
+{
+    public interface IXLWorkbook : IDisposable
+    {
+        String Author { get; set; }
+
+        /// <summary>
+        ///   Gets or sets the workbook's calculation mode.
+        /// </summary>
+        XLCalculateMode CalculateMode { get; set; }
+
+        Boolean CalculationOnSave { get; set; }
+
+        /// <summary>
+        ///   Gets or sets the default column width for the workbook.
+        ///   <para>All new worksheets will use this column width.</para>
+        /// </summary>
+        Double ColumnWidth { get; set; }
+
+        IXLCustomProperties CustomProperties { get; }
+
+        Boolean DefaultRightToLeft { get; }
+
+        Boolean DefaultShowFormulas { get; }
+
+        Boolean DefaultShowGridLines { get; }
+
+        Boolean DefaultShowOutlineSymbols { get; }
+
+        Boolean DefaultShowRowColHeaders { get; }
+
+        Boolean DefaultShowRuler { get; }
+
+        Boolean DefaultShowWhiteSpace { get; }
+
+        Boolean DefaultShowZeros { get; }
+
+        Boolean ForceFullCalculation { get; set; }
+
+        Boolean FullCalculationOnLoad { get; set; }
+
+        Boolean FullPrecision { get; set; }
+
+        Boolean IsPasswordProtected { get; }
+
+        Boolean LockStructure { get; set; }
+
+        Boolean LockWindows { get; set; }
+
+        /// <summary>
+        ///   Gets an object to manipulate this workbook's named ranges.
+        /// </summary>
+        IXLNamedRanges NamedRanges { get; }
+
+        /// <summary>
+        ///   Gets or sets the default outline options for the workbook.
+        ///   <para>All new worksheets will use these outline options.</para>
+        /// </summary>
+        IXLOutline Outline { get; set; }
+
+        /// <summary>
+        ///   Gets or sets the default page options for the workbook.
+        ///   <para>All new worksheets will use these page options.</para>
+        /// </summary>
+        IXLPageSetup PageOptions { get; set; }
+
+        /// <summary>
+        ///   Gets or sets the workbook's properties.
+        /// </summary>
+        XLWorkbookProperties Properties { get; set; }
+
+        /// <summary>
+        ///   Gets or sets the workbook's reference style.
+        /// </summary>
+        XLReferenceStyle ReferenceStyle { get; set; }
+
+        Boolean RightToLeft { get; set; }
+
+        /// <summary>
+        ///   Gets or sets the default row height for the workbook.
+        ///   <para>All new worksheets will use this row height.</para>
+        /// </summary>
+        Double RowHeight { get; set; }
+
+        Boolean ShowFormulas { get; set; }
+
+        Boolean ShowGridLines { get; set; }
+
+        Boolean ShowOutlineSymbols { get; set; }
+
+        Boolean ShowRowColHeaders { get; set; }
+
+        Boolean ShowRuler { get; set; }
+
+        Boolean ShowWhiteSpace { get; set; }
+
+        Boolean ShowZeros { get; set; }
+
+        /// <summary>
+        ///   Gets or sets the default style for the workbook.
+        ///   <para>All new worksheets will use this style.</para>
+        /// </summary>
+        IXLStyle Style { get; set; }
+
+        /// <summary>
+        ///   Gets an object to manipulate this workbook's theme.
+        /// </summary>
+        IXLTheme Theme { get; }
+
+        Boolean Use1904DateSystem { get; set; }
+
+        /// <summary>
+        ///   Gets an object to manipulate the worksheets.
+        /// </summary>
+        IXLWorksheets Worksheets { get; }
+
+        IXLWorksheet AddWorksheet(String sheetName);
+
+        IXLWorksheet AddWorksheet(String sheetName, Int32 position);
+
+        IXLWorksheet AddWorksheet(DataTable dataTable);
+
+        void AddWorksheet(DataSet dataSet);
+
+        void AddWorksheet(IXLWorksheet worksheet);
+
+        IXLWorksheet AddWorksheet(DataTable dataTable, String sheetName);
+
+        IXLCell Cell(String namedCell);
+
+        IXLCells Cells(String namedCells);
+
+        IXLCustomProperty CustomProperty(String name);
+
+        Object Evaluate(String expression);
+
+        IXLCells FindCells(Func<IXLCell, Boolean> predicate);
+
+        IXLColumns FindColumns(Func<IXLColumn, Boolean> predicate);
+
+        IXLRows FindRows(Func<IXLRow, Boolean> predicate);
+
+        IXLNamedRange NamedRange(String rangeName);
+
+        void Protect(Boolean lockStructure, Boolean lockWindows, String workbookPassword);
+
+        void Protect();
+
+        void Protect(string workbookPassword);
+
+        void Protect(Boolean lockStructure);
+
+        void Protect(Boolean lockStructure, Boolean lockWindows);
+
+        IXLRange Range(String range);
+
+        IXLRange RangeFromFullAddress(String rangeAddress, out IXLWorksheet ws);
+
+        IXLRanges Ranges(String ranges);
+
+        /// <summary>
+        ///   Saves the current workbook.
+        /// </summary>
+        void Save();
+
+        /// <summary>
+        ///   Saves the current workbook and optionally performs validation
+        /// </summary>
+        void Save(Boolean validate, Boolean evaluateFormulae = false);
+
+        void Save(SaveOptions options);
+
+        /// <summary>
+        ///   Saves the current workbook to a file.
+        /// </summary>
+        void SaveAs(String file);
+
+        /// <summary>
+        ///   Saves the current workbook to a file and optionally validates it.
+        /// </summary>
+        void SaveAs(String file, Boolean validate, Boolean evaluateFormulae = false);
+
+        void SaveAs(String file, SaveOptions options);
+
+        /// <summary>
+        ///   Saves the current workbook to a stream.
+        /// </summary>
+        void SaveAs(Stream stream);
+
+        /// <summary>
+        ///   Saves the current workbook to a stream and optionally validates it.
+        /// </summary>
+        void SaveAs(Stream stream, Boolean validate, Boolean evaluateFormulae = false);
+
+        void SaveAs(Stream stream, SaveOptions options);
+
+        /// <summary>
+        /// Searches the cells' contents for a given piece of text
+        /// </summary>
+        /// <param name="searchText">The search text.</param>
+        /// <param name="compareOptions">The compare options.</param>
+        /// <param name="searchFormulae">if set to <c>true</c> search formulae instead of cell values.</param>
+        /// <returns></returns>
+        IEnumerable<IXLCell> Search(String searchText, CompareOptions compareOptions = CompareOptions.Ordinal, Boolean searchFormulae = false);
+
+        XLWorkbook SetLockStructure(Boolean value);
+
+        XLWorkbook SetLockWindows(Boolean value);
+
+        XLWorkbook SetUse1904DateSystem();
+
+        XLWorkbook SetUse1904DateSystem(Boolean value);
+
+        Boolean TryGetWorksheet(String name, out IXLWorksheet worksheet);
+
+        void Unprotect();
+
+        void Unprotect(string workbookPassword);
+
+        IXLWorksheet Worksheet(String name);
+
+        IXLWorksheet Worksheet(Int32 position);
+    }
+}
diff --git a/ClosedXML/Excel/XLWorkbook.cs b/ClosedXML/Excel/XLWorkbook.cs
index 5f73324..27ac919 100644
--- a/ClosedXML/Excel/XLWorkbook.cs
+++ b/ClosedXML/Excel/XLWorkbook.cs
@@ -41,7 +41,7 @@
         Simple = 1,
     }
 
-    public partial class XLWorkbook: IDisposable
+    public partial class XLWorkbook: IXLWorkbook
     {
         #region Static