C#读写txt文件的方法

1.添加命名空间

　　System.IO;

　　System.Text;

2.文件的读取

#region 读取TXT文本文件

        /// <summary>
        /// FileStream读取文本文件
        /// </summary>
        public void FileStreamRead()
        {
            //文件路径
            string filePath = AppDomain.CurrentDomain.BaseDirectory;    // Server.MapPath("~/UploadFiles/");

            //文件夹不存在则创建
            if (!System.IO.Directory.Exists(filePath))
            {
                System.IO.Directory.CreateDirectory(filePath);
            }

            filePath = AppDomain.CurrentDomain.BaseDirectory + DateTime.Today.ToString("yyyMMdd") + ".txt";
            if (System.IO.File.Exists(filePath))
            {
                //1.直接读取出字符串
                string strText = System.IO.File.ReadAllText(filePath);

                //2.按行读取为字符串数组
                string[] arrFileText = System.IO.File.ReadAllLines(filePath);

                //3.FileStream读取写入给定的缓存区
                System.IO.FileStream fs = new FileStream(filePath, FileMode.Open);
                fs.Seek(0, SeekOrigin.Begin);
                byte[] byData = new byte[100];
                fs.Read(byData, 0, 100);//byData传进来的字节数组,用以接受FileStream对象中的数据
                System.Text.Decoder d = System.Text.Encoding.Default.GetDecoder();
                char[] charData = new char[1000];
                d.GetChars(byData, 0, byData.Length, charData, 0);
                fs.Close();
            }

            
        }

        /// <summary>
        /// StreamReader读取文本文件
        /// </summary>
        public void StreamReaderRead()
        {
            //文件路径
            string filePath = AppDomain.CurrentDomain.BaseDirectory;    // Server.MapPath("~/UploadFiles/");

            //文件夹不存在则创建
            if (!System.IO.Directory.Exists(filePath))
            {
                System.IO.Directory.CreateDirectory(filePath);
            }

            filePath = AppDomain.CurrentDomain.BaseDirectory + DateTime.Today.ToString("yyyMMdd") + ".txt";
            if (System.IO.File.Exists(filePath))
            {
                //1.从头到尾以流的方式读出文本文件,该方法会读出一行文本
                System.IO.StreamReader sr = new StreamReader(filePath);
                string strStreamReader = sr.ReadToEnd();
                sr.Close();
            }
        }

        #endregion

FileStream fs = new FileStream(@"c:	empascii.txt", FileMode.Open, FileAccess.Read, FileShare.Read);
            //StreamReader sr3 = new StreamReader(fs);
            //string str3 = sr3.ReadToEnd();
            //sr3.Close();
            StreamReader sr4 = new StreamReader(fs, System.Text.Encoding.Default);
            string strCH = sr4.ReadToEnd();
            sr4.Close();
            string str2 = System.IO.File.ReadAllText(@"c:	empascii.txt", System.Text.Encoding.ASCII); 

3.文件的写入

#region 写入TXT文本文件

        /// <summary>
        /// StreamWriter写入文本文件
        /// </summary>
        public void StreamWriterWrite()
        {
            //文件路径
            string filePath = AppDomain.CurrentDomain.BaseDirectory;    // Server.MapPath("~/UploadFiles/");

            //文件不存在则创建
            if (!System.IO.Directory.Exists(filePath))
            {
                System.IO.Directory.CreateDirectory(filePath);
            }
            filePath = AppDomain.CurrentDomain.BaseDirectory + DateTime.Today.ToString("yyyMMdd") + ".txt";

            #region 另一种方式
            ////FileMode.Append,FileAccess.Write追加文件
            //FileStream fs = new FileStream(filePath, FileMode.OpenOrCreate);
            //StreamWriter sw = new StreamWriter(fs);

            #endregion

            StreamWriter sw = new StreamWriter(filePath, true);
            //Write直接追加文件末尾，不换行;WriteLine直接追加文件末尾，换行
            sw.WriteLine("测试StreamWriter写入TXT文件" + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss:ffff"));
            
            //清空缓冲区、关闭流
            sw.Flush();
            sw.Close();
            
            //直接追加到文件
            //using (System.IO.StreamWriter sw = System.IO.File.AppendText(filePath))
            //{
            //    sw.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss:ffff"));
            //}

        }

        /// <summary>
        /// FileStream写入文本文件
        /// </summary>
        public void FileStreamWrite()
        {
            //文件路径
            string filePath = AppDomain.CurrentDomain.BaseDirectory;    // Server.MapPath("~/UploadFiles/");

            //文件不存在则创建
            if (!System.IO.Directory.Exists(filePath))
            {
                System.IO.Directory.CreateDirectory(filePath);
            }
            filePath = AppDomain.CurrentDomain.BaseDirectory + DateTime.Today.ToString("yyyMMdd") + ".txt";

            //1.该方法写入字符数组换行显示
            string[] arrFile = { "first line", "second line", "third line", "第四行" };
            System.IO.File.AppendAllLines(filePath, arrFile, System.Text.Encoding.Default);

            //2.字符串写入文本
            string strTest = "该例子测试一个字符串写入文本文件。";
            System.IO.File.AppendAllText(filePath, strTest, System.Text.Encoding.Default);

            //3.FileMode.Append,FileAccess.Write追加文件
            FileStream fs = new FileStream(filePath, FileMode.Append,FileAccess.Write);
            byte[] data = System.Text.Encoding.Default.GetBytes("测试FileStream写入TXT文件" + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss:ffff"));
            fs.Write(data, 0, data.Length);
            //清空缓冲区、关闭流
            fs.Flush();
            fs.Close();
        }

        #endregion

#region 读取 保存

                ////读取
                //string strFileTxt = string.Empty;
                //using (FileStream fs = new FileStream(strFileName, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
                //{
                //    StreamReader sr = new StreamReader(fs, System.Text.Encoding.UTF8);   //选择编码方式  
                //    strFileTxt = sr.ReadToEnd();
                //}

                ////保存
                //using (FileStream fs = new FileStream(strSavePath, FileMode.Create, FileAccess.Write))
                //{
                //    byte[] fData = Encoding.UTF8.GetBytes(strFileTxt);
                //    fs.Write(fData, 0, fData.Length);
                //    fs.Flush();
                //}

                #endregion

http://www.cnblogs.com/jx270/archive/2013/04/14/3020456.html