protected DataTable ExcelToDT(string fileName)
        {
            string str = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + fileName +
                         ";Extended Properties=\"Excel 12.0 Xml;HDR=YES;IMEX=1\"";

            OleDbConnection conn = new OleDbConnection(str);
            DataTable exceldt = new DataTable();
            try
            {
                conn.Open();
                DataTable tableschema = conn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);//获取excel表中的标题
                string sheetname = tableschema.Rows[0][2].ToString().Trim();//获取excel表中第一个Sheet的名称
                string oledbstr = "select * from [" + sheetname + "]";
                OleDbCommand com = new OleDbCommand(oledbstr, conn);
                OleDbDataAdapter adp = new OleDbDataAdapter(com);
                adp.Fill(exceldt);
                conn.Close();
                File.Delete(fileName);
                exceltodata = true;
            }
            catch
            {
                //显示错误信息
                //throw(e);
                exceltodata = false;
            }
            finally
            {
                if (conn.State == ConnectionState.Open)
                {
                    conn.Close();
                }
            }
            return exceldt;
        }