C#操作Excel替换关键字

        /// <summary>
        /// 查找替换关键字
        /// </summary>
        /// <param name="fileName">文件名</param>
        private void FindWord(string fileName)
        {
            Excel.Application ep = new Excel.ApplicationClass();
            try
            {
                object MissingValue = Type.Missing;
                string strKeyWord = txtFindWord.Text.Trim();    //指定要搜索的文本，如果有多个，则声明string[]
                Excel.Workbook ew = ep.Workbooks.Open(fileName, MissingValue,
                            MissingValue, MissingValue, MissingValue,
                            MissingValue, MissingValue, MissingValue,
                            MissingValue, MissingValue, MissingValue,
                            MissingValue, MissingValue, MissingValue,
                            MissingValue);

                Excel.Worksheet ews;
                int iEWSCnt = ew.Worksheets.Count;
                Excel.Range oRange;
                object oText = strKeyWord.Trim().ToUpper();

                for (int i = 1; i <= iEWSCnt; i++)
                {
                    ews = null;
                    ews = (Excel.Worksheet)ew.Worksheets[i];

                    oRange = null;
                    oRange = ((Excel.Range)ews.UsedRange).Find(
                    oText, MissingValue, MissingValue,
                    MissingValue, MissingValue, Excel.XlSearchDirection.xlNext,
                    MissingValue, MissingValue, MissingValue);
                    if (oRange != null && oRange.Cells.Rows.Count >= 1 && oRange.Cells.Columns.Count >= 1)
                    {
                        oRange.Replace(oText, txtReplace.Text, MissingValue, MissingValue, MissingValue, MissingValue, MissingValue, MissingValue);
                        ew.Save();
                    }
                }
                ep.Quit();
            }
            catch
            {
                ep.Quit();
            }
        }