Optimize C# method that compares and creates a differences Excel file

This question is related to my previous question Link The method bellow does excatly what I need, but I need to make it run faster. Does anyone have any suggestion? Thanks.

        public bool createReport_NewMinusBase(string currentWorkingDirectory, string Book1, string Book2, double tolerance)
        {
            tolerance = 0.0001;
            myExcel.Application excelApp = new myExcel.Application();  // Creates a new Excel Application
            excelApp.Visible = false;  // Makes Excel visible to the user.
            excelApp.Application.DisplayAlerts = false;

            //useful for COM object interaction
            object missing = System.Reflection.Missing.Value;

            //Return value
            bool wereDifferences = false;

            //Comparison objects
            object objNew = null;
            object objBase = null;


            //source: http://www.codeproject.com/KB/office/csharp_excel.aspx
            //xlApp.Workbooks.Open(reportFolder + reportName, 0, false, 5, "", "", false, myExcel.XlPlatform.xlWindows, "", true, false, 0, true, false, false);

            //Open BASE FILE
            myExcel.Workbook excelWorkbook1 = excelApp.Workbooks.Open(@currentWorkingDirectory + Book1, 0,
                                              missing, missing, missing, missing, missing, missing, 
                                              missing,missing, missing, missing, missing, missing, missing);
            //OPEN NEW FILE
            myExcel.Workbook excelWorkbook2 = excelApp.Workbooks.Open(@currentWorkingDirectory + Book2, 0, 
                                              missing, missing, missing, missing, missing, missing, 
                                              missing, missing, missing, missing, missing, missing, missing);

            myExcel.Workbook excelWorkbook3 = excelApp.Application.Workbooks.Add(myExcel.XlWBATemplate.xlWBATWorksheet);

            myExcel.Worksheet wsBase;
            myExcel.Worksheet wsDiff;
            myExcel.Worksheet wsNew;


            try
            {
                wsBase = (myExcel.Worksheet)excelApp.Workbooks[Book1].Sheets["Sheet1"];
                wsNew = (myExcel.Worksheet)excelApp.Workbooks[Book2].Sheets["Sheet1"];
                wsDiff = (myExcel.Worksheet)excelWorkbook3.Worksheets.get_Item(1);
            }
            catch
            {
                throw new Exception("Excel file does not contain properly formatted worksheets");

            }


            //Copy Sheet from Excel Book "NEW" to "NEW(-)BASE"
            myExcel.Worksheet source_sheet;
            source_sheet = (myExcel.Worksheet)excelApp.Workbooks[Book2].Sheets["Sheet1"];
            source_sheet.UsedRange.Copy();
            wsDiff.Paste();




            //Determine working area
            int row = 0;
            int col = 0;
            int maxR = 0;
            int maxC = 0;

            int lr1 = 0;
            int lr2 = 0;
            int lc1 = 0;
            int lc2 = 0;
            {
                lr1 = wsNew.UsedRange.Rows.Count;
                lc1 = wsNew.UsedRange.Columns.Count;
            }

            {
                lr2 = wsBase.UsedRange.Rows.Count;
                lc2 = wsBase.UsedRange.Columns.Count;
            }

            maxR = lr1;
            maxC = lc1;

            if (maxR < lr2) maxR = lr2;
            if (maxC < lc2) maxC = lc2;

            //===================================================
            //Compare Cells
            //===================================================

            for (row = 1; row <= maxR; row++)
            {
                for (col = 1; col <= maxC; col++)
                {
                    //Get cell values
                    objNew = ((myExcel.Range)wsNew.Cells[row, col]).Value2;
                    objBase = ((myExcel.Range)wsBase.Cells[row, col]).Value2;


                    //If they are not equivilante
                    if (!equiv(objNew, objBase, tolerance))
                    {
                        wereDifferences = true;

                        //Mark differing cells
                        ((myExcel.Range)wsNew.Cells[row, col]).Interior.Color = System.Drawing.ColorTranslator.ToOle(System.Drawing.Color.Red);
                        ((myExcel.Range)wsBase.Cells[row, col]).Interior.Color = System.Drawing.ColorTranslator.ToOle(System.Drawing.Color.Red);

                        if ((objNew == null))
                        {                            
                            ((myExcel.Range)wsDiff.Cells[row, col]).Interior.Color = System.Drawing.ColorTranslator.ToOle(System.Drawing.Color.Red);
                        }
                        else if (objNew.GetType().ToString() == "System.String")
                        {
                            ((myExcel.Range)wsDiff.Cells[row, col]).Interior.Color = System.Drawing.ColorTranslator.ToOle(System.Drawing.Color.Red);
                        }
                        else
                        {
                            ((myExcel.Range)wsDiff.Cells[row, col]).Interior.Color = System.Drawing.ColorTranslator.ToOle(System.Drawing.Color.Yellow);
                            ((myExcel.Range)wsDiff.Cells[row, col]).Value2 = ((myExcel.Range)wsNew.Cells[row, col]).Value2 - ((myExcel.Range)wsBase.Cells[row, col]).Value2;
                        }
                    }
                    else //They are equivalent
                    {                        
                        if ((objNew == null))
                        {
                        }
                        else if (objNew.GetType().ToString() == "System.String")
                        {
                        }
                        else
                        {                            
                            ((myExcel.Range)wsDiff.Cells[row, col]).Value2 = ((myExcel.Range)wsNew.Cells[row, col]).Value2 - ((myExcel.Range)wsBase.Cells[row, col]).Value2;
                        }
                    }
                }
            }


            // Copy formatting
            myExcel.Range range1 = wsBase.get_Range((myExcel.Range)wsBase.Cells[1, 1], (myExcel.Range)wsBase.Cells[maxR, maxC]);
            myExcel.Range range2 = wsDiff.get_Range((myExcel.Range)wsDiff.Cells[1, 1], (myExcel.Range)wsDiff.Cells[maxR, maxC]);
            range1.Copy();
            range2.PasteSpecial(myExcel.XlPasteType.xlPasteColumnWidths);

            excelApp.Workbooks[Book1].Close(false, false, false);
            excelApp.Workbooks[Book2].Close(false, false, false);

            string Book3 = "reporttestpc.xlsx"; //"reportBaseMinusNew.xlsx"
            if (File.Exists(currentWorkingDirectory + Book3))
            {
                File.Delete(currentWorkingDirectory + Book3);
            }

            excelWorkbook3.SaveAs(currentWorkingDirectory + Book3, Type.Missing, Type.Missing,
                                 Type.Missing, false, false, myExcel.XlSaveAsAccessMode.xlNoChange,
                                 Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);

            //excelApp.Workbooks[Book3].Close(false, false, false);

            excelApp.Visible = true;
            return wereDifferences;
        }


        /// Determines whether two objects are equivalent
        /// Numbers are equivalent within the specified tolerance
        /// Strings are equivalent if they are identical
        /// obj1 and obj2 are the two objects being compared
        /// tolerance is the maximum difference between two numbers for them to be deemed equivalent

        private bool equiv(object obj1, object obj2, double tolerance)
        {
            if ((obj1 == null) && (obj2 == null))
            {
                return true;
            }
            else if ((obj1 == null) || (obj2 开发者_C百科== null))
            {
                return false;
            }

            //if both are numeric
            if (IsNumeric(obj1))
            {
                if (IsNumeric(obj2))
                {
                    if (Math.Abs(Convert.ToDouble(obj2) - Convert.ToDouble(obj1)) < tolerance)
                    {
                        return true;    //If they are within tolerance
                    }
                    else
                    {
                        return false;   //If they are outside tolerance
                    }
                }
                else
                {
                    return false;       //If only one is numeric
                }
            }

            //Now assuming both are just random strings
            else
            {
                if ((string)obj1 == (string)obj2)
                {
                    return true;
                }
                else
                {
                    return false;
                }
            }
        }


        // Test whether a given object represents a number
        internal static bool IsNumeric(object ObjectToTest)
        {
            if (ObjectToTest == null)
            {
                return false;
            }
            else
            {
                double OutValue;
                return double.TryParse(ObjectToTest.ToString().Trim(),
                    System.Globalization.NumberStyles.Any,
                    System.Globalization.CultureInfo.CurrentCulture,
                    out OutValue);
            }
        }

    ///

---

Suggestion 1:

Make:

objNew.GetType().ToString() == "System.String"

This:

objNew is string

Alot cleaner, right? Should be faster too.

Suggestion 2:

You make this call alot:

((myExcel.Range)wsDiff.Cells[row, col]

Store the result in a variable and reuse it. All those indexers, properties, and boxing/unboxing will have overhead. Same goes for any place you are accessing the same COM method, property, or indexer over and over. Make sure you declare these variables outside of the scope of your for-loops also, you will hurt performance if they go in and out of scope for each iteration of the loop.

Suggestion 3:

Can you reuse your Excel Application object? Looks like you make a new one every time this method is called. Can you store it in a member variable in your class?

---

You can try using OleDb to read and write the excel documents.

I don't know how the performance compares, but you can profile for that.

---

I think your IsNumeric() function is doing a lot of work. How about simply testing the object's type?

if(ObjectToTest == null) return false;  
else if(ObjectToTest.GetType() == typeof(double)) return Convert.ToDouble(ObjectToTest);  
else if(ObjectToTest.GetType() == typeof(decimal)) return Convert.ToDouble(ObjectToTest);  
else return false;

Also, I think you only have to test for doubles and decimals. I may be wrong.