c# Csv文件读写示例，如果文件存在追加写入

功能

        1.写入

        2.读取

导出文件效果

调用示例

注意示例中的ToDataTable()方法是自己的封装的扩展方法，源码在集合扩展方法-CSDN博客

private List<MarkDataModel> createMarkDataList(int count){var markDataModels = new List<MarkDataModel>();for (int i = 0; i < count; i++){markDataModels.Add(new MarkDataModel(){X = i + 1,Y = i + 1,Text = "Data" + i + "_" + DateTime.Now.ToString("HHmmssfff")});}return markDataModels;}/// <summary>/// 写入/// </summary>/// <param name="sender"></param>/// <param name="e"></param>private void btnWrite_Click(object sender, EventArgs e){var dataList = createMarkDataList(10);//var filePath = AppContext.BaseDirectory + @"WeldResultUpload\" + DateTime.Now.ToString("yyyyMMdd") + @"\" + Global.GlobalIns.MaterialsCodeCurrent + ".xlsx";string currentDirectory = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);currentDirectory += @"ResultUpload\" + DateTime.Now.ToString("yyyyMMdd") + ".csv";CsvHelper.SaveCSV(dataList.ToDataTable(), currentDirectory);var dataList2 = createMarkDataList(20);CsvHelper.SaveCSV(dataList2.ToDataTable(), currentDirectory);MessageBox.Show("导出完成");}

Csv文件帮助类

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Text;
using System.IO;namespace CSVWinFormsApp
{/// <summary>/// Csv文件帮助类/// </summary>public class CsvHelper{/// <summary>/// 写入CSV文件/// </summary>/// <param name="dt">要写入的数据表</param>/// <param name="fullPath">保存的文件路径，注意包含文件名</param>public static void SaveCSV(DataTable dt, string fullPath){try{FileInfo fi = new FileInfo(fullPath);//判断文件目录是否存在if (!fi.Directory.Exists){//如果目录不存在就创建目录fi.Directory.Create();}var isExists = File.Exists(fullPath);//FileMode.Append 如果文件存在追加写入using (FileStream fs = new FileStream(fullPath, FileMode.Append,FileAccess.Write)){StreamWriter sw = new StreamWriter(fs, System.Text.Encoding.UTF8);string data = string.Empty;if (!isExists){for (int i = 0; i < dt.Columns.Count; i++)//写入列名{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++) //写入各行数据{data = string.Empty;for (int j = 0; j < dt.Columns.Count; j++){string str = dt.Rows[i][j].ToString();str = str.Replace("\"", "\"\"");//替换英文冒号 英文冒号需要换成两个冒号if (str.Contains(',') || str.Contains('"')|| str.Contains('\r') || str.Contains('\n')) //含逗号 冒号 换行符的需要放到引号中{str = string.Format("\"{0}\"", str);}data += str;if (j < dt.Columns.Count - 1){data += ",";}}sw.WriteLine(data);}//使用了Using可以不手动关闭了。好买书还是关一下的好sw.Close();fs.Close();}}catch (Exception ex){}}/// <summary>/// 打开CSV文件/// </summary>/// <param name="filePath"></param>/// <returns></returns>public static DataTable OpenCSV(string filePath)//从csv读取数据返回table{System.Text.Encoding encoding = GetType(filePath); //Encoding.ASCII;//DataTable dt = new DataTable();try{using (FileStream fs = new FileStream(filePath, FileMode.Open,FileAccess.Read)){StreamReader sr = new StreamReader(fs, encoding);//记录每次读取的一行记录string strLine = string.Empty;//记录每行记录中的各字段内容string[] aryLine = null;string[] tableHead = null;//标示列数int columnCount = 0;//标示是否是读取的第一行bool IsFirst = true;//逐行读取CSV中的数据while ((strLine = sr.ReadLine()) != null){if (IsFirst == true){tableHead = strLine.Split(',');IsFirst = false;columnCount = tableHead.Length;//创建列for (int i = 0; i < columnCount; i++){DataColumn dc = new DataColumn(tableHead[i]);dt.Columns.Add(dc);}}else{aryLine = strLine.Split(',');DataRow dr = dt.NewRow();for (int j = 0; j < columnCount; j++){dr[j] = aryLine[j];}dt.Rows.Add(dr);}}if (aryLine != null && aryLine.Length > 0){dt.DefaultView.Sort = tableHead[0] + " " + "asc";}//使用了Using可以不手动关闭了。好买书还是关一下的好sr.Close();fs.Close();}}catch (Exception ex){}return dt;}/// <summary>/// 给定文件的路径，读取文件的二进制数据，判断文件的编码类型/// </summary>/// <param name="FILE_NAME">文件路径</param>/// <returns>文件的编码类型</returns>public static System.Text.Encoding GetType(string FILE_NAME){FileStream fs = new FileStream(FILE_NAME, FileMode.Open,FileAccess.Read);System.Text.Encoding r = GetType(fs);fs.Close();return r;}/// <summary>/// 通过给定的文件流，判断文件的编码类型/// </summary>/// <param name="fs">文件流</param>/// <returns>文件的编码类型</returns>public static System.Text.Encoding GetType(FileStream fs){byte[] Unicode = new byte[] { 0xFF, 0xFE, 0x41 };byte[] UnicodeBIG = new byte[] { 0xFE, 0xFF, 0x00 };byte[] UTF8 = new byte[] { 0xEF, 0xBB, 0xBF }; //带BOMSystem.Text.Encoding reVal = System.Text.Encoding.Default;BinaryReader r = new BinaryReader(fs, System.Text.Encoding.Default);int i;int.TryParse(fs.Length.ToString(), out i);byte[] ss = r.ReadBytes(i);if (IsUTF8Bytes(ss) || (ss[0] == 0xEF && ss[1] == 0xBB && ss[2] == 0xBF)){reVal = System.Text.Encoding.UTF8;}else if (ss[0] == 0xFE && ss[1] == 0xFF && ss[2] == 0x00){reVal = System.Text.Encoding.BigEndianUnicode;}else if (ss[0] == 0xFF && ss[1] == 0xFE && ss[2] == 0x41){reVal = System.Text.Encoding.Unicode;}r.Close();return reVal;}/// <summary>/// 判断是否是不带 BOM 的 UTF8 格式/// </summary>/// <param name="data"></param>/// <returns></returns>private static bool IsUTF8Bytes(byte[] data){int charByteCounter = 1;  //计算当前正分析的字符应还有的字节数byte curByte; //当前分析的字节.for (int i = 0; i < data.Length; i++){curByte = data[i];if (charByteCounter == 1){if (curByte >= 0x80){//判断当前while (((curByte <<= 1) & 0x80) != 0){charByteCounter++;}//标记位首位若为非0 则至少以2个1开始 如:110XXXXX...........1111110X　if (charByteCounter == 1 || charByteCounter > 6){return false;}}}else{//若是UTF-8 此时第一位必须为1if ((curByte & 0xC0) != 0x80){return false;}charByteCounter--;}}if (charByteCounter > 1){throw new Exception("非预期的byte格式");}return true;}}
}

集合数据Model

/// <summary>/// 打标数据 Model/// </summary>public class MarkDataModel{/// <summary>/// 坐标X/// </summary>[Description("坐标X")]//可以自定义中文列名public double X { get; set; }/// <summary>/// 坐标Y/// </summary>public double Y { get; set; }/// <summary>/// 打标数据/// </summary>public string Text { get; set; }}