数据流读、写、删、修CSV文件

　　 class CSVFileOperation
    {
        private string fileFullName;//CSV文件路径，包括文件名、扩展名    

        public CSVFileOperation(string fileFullName)
        {
            this.fileFullName = fileFullName;
        }

        //注意FileMode：Create和CreateNew的区别
        public void WriteFile(DataTable dt)
        {            
            FileStream fs = new FileStream(fileFullName, System.IO.FileMode.Create, System.IO.FileAccess.Write);
            StreamWriter sw = new StreamWriter(fs, System.Text.Encoding.Default);
            string data = "";
            for (int i = 0; i < dt.Columns.Count; i++)//写出列名称，实际也是写入一行
            {
                data += dt.Columns[i].ColumnName.ToString();
                if (i < dt.Columns.Count - 1)
                {
                    data += ",";
                }
            }
            sw.WriteLine(data);
            for (int i = 0; i < dt.Rows.Count; i++)//写出各行数据
            {
                data = "";
                for (int j = 0; j < dt.Columns.Count; j++)
                {
                    data += dt.Rows[i][j].ToString();//将数据均已字符串个数输出
                    if (j < dt.Columns.Count - 1)//每行末不需要加","
                    {
                        data += ",";
                    }
                }
                sw.WriteLine(data);
            }
            sw.Close();
            fs.Close();            
        }

        /// <summary>
        /// 创建一个新的CSV文件，只包含列名，表格的行数为0
        /// </summary>
        /// <param name="colNames">包含列名的数组，列的个数等于数组的长度</param>
        public void CreateNewFile(string[] colNames)
        {
            if (File.Exists(fileFullName))
            {
                DialogResult result = MessageBox.Show("您想创建的文件已经存在，是否要覆盖？", "提示", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
                if (!(result == DialogResult.Yes))
                {
                    MessageBox.Show("退出创建新文件", "提示");
                    return;
                }
            }
            FileStream fs = new FileStream(fileFullName, System.IO.FileMode.Create, System.IO.FileAccess.Write);
            StreamWriter sw = new StreamWriter(fs, System.Text.Encoding.Default);

            string data = "";
            for (int j = 0; j < colNames.Length; j++)
            {
                data += colNames[j].ToString();
                if (j < colNames.Length - 1)
                {
                    data += ",";
                }
            }
            sw.WriteLine(data);
            sw.Close();
            fs.Close();
            MessageBox.Show("创建了一个新CSV文件，仅包括标题行！");
        }

        /// <summary>
        /// 将CSV文件的数据读取到DataTable中
        /// </summary>
        /// <returns>将文件数据以DataTable形式返回</returns>
        public DataTable ReadFileData()
        {            
            DataTable dt = new DataTable();
            FileStream fs = new FileStream(fileFullName, System.IO.FileMode.Open, System.IO.FileAccess.Read);
            StreamReader sr = new StreamReader(fs, System.Text.Encoding.Default);
            string strLine = "";//记录每次读取的一行记录
            string[] aryLine;//记录每行记录中的各字段内容
            int columnCount = 0;//标示列数
            bool IsFirst = true; //标示是否是读取的第一行
            while ((strLine = sr.ReadLine()) != null)//逐行读取CSV中的数据
            {
                aryLine = strLine.Split(‘,‘);//逗号分割字符串
                if (IsFirst == true)
                {
                    IsFirst = false;
                    columnCount = aryLine.Length;//创建列                    
                    for (int i = 0; i < columnCount; i++)
                    {
                        DataColumn dc = new DataColumn(aryLine[i]);
                        dt.Columns.Add(dc);
                    }
                }
                else
                {
                    DataRow dr = dt.NewRow();
                    for (int j = 0; j < columnCount; j++)
                    {
                        dr[j] = aryLine[j];
                    }
                    dt.Rows.Add(dr);
                }
            }
            sr.Close();
            fs.Close();
            return dt;
        }

        public int GetColsNum()
        {
            FileStream fs = new FileStream(fileFullName, System.IO.FileMode.Open, System.IO.FileAccess.Read);
            StreamReader sr = new StreamReader(fs, System.Text.Encoding.Default);
            string strLine = "";//记录每次读取的一行记录
            string[] aryLine;//记录每行记录中的各字段内容
            int columnCount = 0;//标示列数
            if ((strLine = sr.ReadLine()) != null)
            {
                aryLine = strLine.Split(‘,‘);//逗号分割字符串                
                columnCount = aryLine.Length;//创建列                                  
            }
            sr.Close();
            fs.Close();
            return columnCount;
        }

        /// <summary>
        /// 得到当前文件的行数，不含标题行
        /// </summary>
        /// <returns>行数</returns>
        public int  GetRowsNum()
        {
            FileStream fs = new FileStream(fileFullName, System.IO.FileMode.Open, System.IO.FileAccess.Read);
            StreamReader sr = new StreamReader(fs, System.Text.Encoding.Default);
            int RowCount = 0;//标示列数
            while (sr.ReadLine() != null)
            {
                RowCount++;
            }
            sr.Close();
            fs.Close();
            return RowCount - 1;//实际行数不包含标题行
        }

        /// <summary>
        /// 在存在的文件后面添加一行
        /// </summary>
        /// <param name="str">添加行的字符数组</param>
        /// <returns>返回当前操作是否成功</returns>
        public bool AppendLine(string[] str)
        {
            //注意：FileMode打开文件的方式修改为Append    
            if (File.Exists(fileFullName) == false)//如果文件不存在则创建新的文件
            {
                return false;
            }

            FileStream fs = new FileStream(fileFullName, System.IO.FileMode.Append, System.IO.FileAccess.Write);
            StreamWriter sw = new StreamWriter(fs, System.Text.Encoding.Default);
            string data = "";
            for (int j = 0; j < str.Length; j++)
            {
                data += str[j].ToString();
                if (j < str.Length - 1)
                {
                    data += ",";
                }
            }
            sw.WriteLine(data);
            sw.Close();
            fs.Close();
            return true;
        }

        /// <summary>
        /// 删除行
        /// </summary>
        /// <param name="rowNum">实际行数（1...总行数）</param>
        /// <returns></returns>
        public bool DeleteLine(int rowNum)
        {
            if (rowNum > this.GetRowsNum() || rowNum < 1)
            {
                return false;
            }

            DataTable dt = this.ReadFileData();
            dt.Rows.RemoveAt(rowNum - 1);//删除rowNum行
            try
            {
                this.WriteFile(dt);
                return true;
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "异常");
                return false;
            }
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="rowNum"></param>
        /// <param name="str"></param>
        /// <returns></returns>
        public bool ModificationLine(int rowNum, string[] str)
        {
            if (rowNum > this.GetRowsNum() || rowNum < 1)
            {
                return false;
            }

            DataTable dt = this.ReadFileData();
            dt.Rows.RemoveAt(rowNum - 1);//删除rowNum行
            DataRow dr = dt.NewRow();
            for (int i = 0; i < str.Length; i++)
            {
                dr[i] = str[i];
            }
            dt.Rows.InsertAt(dr, rowNum - 1);           
            try
            {
                this.WriteFile(dt);
                return true;
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "异常");
                return false;
            }
        }
    }