C#中的各种流

//Stream是一个抽象类，不能直接实例化
        //FileStream继承于Stream ,读写文件流        
        //StreamWriter继承于TextWriter(抽象类，继承于MarshalByRefObject, IDisposable)，可以操作Stream
        //StreamReader继承于TextReader(抽象类，继承于MarshalByRefObject, IDisposable)，可以操作Stream
        //MemoryStream继承于Stream 
        //BufferedStream继承于Stream       

      StreamWriter和StreamReader可以直接操作文件进行读写，但前提是文件是已经存在的，如果没有文件存在，会抛出异常。

        //文件流操作
        private void btnFileStream_Click(object sender, EventArgs e)
        {
            string path=@"c:\test.txt";

            #region FileStream 读写文件必须以字节形式 
            //向文件中写入流
            using (FileStream fs = File.Create(path))
            {                
                //byte[] info = new UTF8Encoding(true).GetBytes("this is some text");
                Byte[] info = Encoding.GetEncoding("UTF-8").GetBytes("this is some text");
                fs.Write(info, 0, info.Length);
            }

            //打开文件读回流
            using (FileStream fs = File.OpenRead(path))
            {
                string result = string.Empty;
                byte[] info = new byte[1024];
                //UTF8Encoding temp = new UTF8Encoding(true);
                while (fs.Read(info, 0, info.Length) > 0)
                {
                    //result += temp.GetString(info);
                    result += Encoding.GetEncoding("UTF-8").GetString(info);
                }
                System.Diagnostics.Debug.WriteLine(result);
            }

            #endregion

            #region StreamWriter 以字符的形式写入 1.可以往Stream里写，2.也可以直接往路径文件里写信息(前提是文件已存在)

            //打开文件，在文件末尾附加信息
            FileStream fileStream = new FileStream(path,FileMode.Append);
            StreamWriter sw = new StreamWriter(fileStream);
            sw.WriteLine("This is the appended line.");
            sw.Close();
            fileStream.Close();

            //打开文件，在文件末尾附加信息
            using (FileStream file = new FileStream(path, FileMode.Append))
            {
                using (StreamWriter writer = new StreamWriter(file))
                //using (StreamWriter writer = new StreamWriter(path))
                {
                    writer.WriteLine("this a the second appended line.");
                    writer.Write("this a the third appended line.");
                }
            }

             //如果文件已经存在，可以及直接用StreamWriter写入，不用File

             //using (StreamWriter writer = new StreamWriter(path))
             // {
                   // writer.WriteLine("this a the second appended line.");
                   // writer.Write("this a the third appended line.");
              // }

            #endregion

            #region StreamReader 1.可以从Stream里读，2.也可以直接从文件里读信息

            //读取文件文本内容 1
            using (StreamReader reader = new StreamReader(path,Encoding.UTF8))
            {
                string line;
                while ((line = reader.ReadLine()) != null)
                {
                    System.Diagnostics.Debug.WriteLine(line);
                }
            }

            //读取文件文本内容 2
            using(FileStream fs1=File.OpenRead(path))
            {
                using (StreamReader reader = new StreamReader(fs1,Encoding.GetEncoding("GB2312")))
                {
                    string result = reader.ReadToEnd();
                    System.Diagnostics.Debug.WriteLine(result);
                }
            }

            #endregion

            #region 内存流，可读可写，操作单位是字节，主要作用是在内存中操作字节流，最后可写入到Stream中
            
            using (MemoryStream ms = new MemoryStream())
            {
                UnicodeEncoding uniEncoding = new UnicodeEncoding();
                byte[] info = uniEncoding.GetBytes(" this is MemoryStream");
                
                //把信息写入到MemoryStream中
                ms.Write(info, 0, info.Length);

                byte[] result=new byte[ms.Length];
                //从流中读取信息到字节数组中
                ms.Read(result, 0, info.Length);

                using (Stream s = new FileStream("c:/aa.txt",FileMode.Create))
                {
                    //可以将内存流写入到Stream中：this is MemoryStream
                    ms.WriteTo(s);                    
                }
            }
            #endregion

            //缓冲区是内存中的字节块，用于缓存数据，从而减少对操作系统的调用次数。 缓冲区可提高读取和写入性能。
            //BufferedStream
        }

 

写日志：

            SaveFileDialog saveFileDialog = new SaveFileDialog();
            saveFileDialog.Filter = "log files(*.log)|*.log|txt files(*.txt)|*.txt|All files(*.*)|*.*";
            saveFileDialog.FilterIndex = 0;
            saveFileDialog.RestoreDirectory = true;
            saveFileDialog.FileName = DateTime.Now.ToString("yyyyMMddHHmmss") + ".log";
            FileStream fs = null;
            StreamWriter sw = null;
            if (saveFileDialog.ShowDialog() == DialogResult.OK)
            {
                try
                {
                    fs = (FileStream)saveFileDialog.OpenFile();
                    sw = new StreamWriter(fs);
                    sw.Write(txtImportLog.Text);
                }
                catch (Exception ex)
                {
                    MessageBox.Show("日志导出失败!" + ex.Message);
                }
                finally
                {
                    sw.Flush();
                    sw.Close();
                    fs.Close();
                }
            }