CSV ⇒　EXCEL　エクセルファイルを確認すると「001」が「1」と表示されます。

    private static void OneMethod() {
        Excel.Application xlApplication = null;

        try {
            xlApplication = new Excel.Application();
            xlApplication.SheetsInNewWorkbook = 1;
            Excel.Workbooks xlBooks = null;

            try {
                xlBooks = xlApplication.Workbooks;
                Excel.Workbook xlBook = null;

                try {
                    string stFilePath = System.IO.Path.Combine("D" + System.IO.Path.VolumeSeparatorChar, "MakiMakiLove.csv");
                    xlBook = xlBooks.Add(System.Reflection.Missing.Value);
                    Excel.Sheets xlSheets = null;

                    try {
                        xlSheets = xlBook.Sheets;
                        Excel.Worksheet xlSheet = null;

                        try {
                            xlSheet = (Excel.Worksheet)xlSheets[1];
                            Excel.Range xlCells = null;

                            try {
                                xlCells = xlSheet.Cells;

                                using (System.IO.StreamReader sr = new System.IO.StreamReader(stFilePath, System.Text.Encoding.Default)) {
                                    try {
                                        int iRow = 1;

                                        while (sr.Peek() >= 0) {
                                            string[] stLines = sr.ReadLine().Split(',');
                                            int iColumn = 1;

                                            foreach (string stItem in stLines) {
                                                Excel.Range xlRange = null;
                                                
                                                try {
                                                    xlRange = (Excel.Range)xlCells[iRow, iColumn];
                                                    xlRange.NumberFormatLocal = "@";
                                                    xlRange.Value2 = stItem;
                                                    iColumn++;
                                                } finally {
                                                    if (xlRange != null) {
                                                        System.Runtime.InteropServices.Marshal.ReleaseComObject(xlRange);
                                                    }
                                                }
                                            }

                                            iRow++;
                                        }
                                    } finally {
                                        if (sr != null) {
                                            sr.Close();
                                        }
                                    }
                                }
                            } finally {
                                if (xlCells != null) {
                                    System.Runtime.InteropServices.Marshal.ReleaseComObject(xlCells);
                                }
                            }
                        } finally {
                            if (xlSheet != null) {
                                System.Runtime.InteropServices.Marshal.ReleaseComObject(xlSheet);
                            }
                        }
                    } finally {
                        if (xlSheets != null) {
                            System.Runtime.InteropServices.Marshal.ReleaseComObject(xlSheets);
                        }
                    }

                    xlBook.SaveAs (
                        System.IO.Path.ChangeExtension(stFilePath, "xls"),
                        System.Reflection.Missing.Value, System.Reflection.Missing.Value,
                        System.Reflection.Missing.Value, System.Reflection.Missing.Value, System.Reflection.Missing.Value,
                        Excel.XlSaveAsAccessMode.xlNoChange, System.Reflection.Missing.Value, System.Reflection.Missing.Value,
                        System.Reflection.Missing.Value, System.Reflection.Missing.Value, System.Reflection.Missing.Value
                    );
                } finally {
                    if (xlBook != null) {
                        try {
                            xlBook.Close(System.Reflection.Missing.Value, System.Reflection.Missing.Value, System.Reflection.Missing.Value);
                        } finally {
                            System.Runtime.InteropServices.Marshal.ReleaseComObject(xlBook);
                        }
                    }
                }
            } finally {
                if (xlBooks != null) {
                    System.Runtime.InteropServices.Marshal.ReleaseComObject(xlBooks);
                }
            }
        } finally {
            if (xlApplication != null) {
                try {
                    xlApplication.Quit();
                } finally {
                    System.Runtime.InteropServices.Marshal.ReleaseComObject(xlApplication);
                }
            }
　　    }
    }