//读取private void button1_Click(object sender, EventArgs e){using (StreamReader sr = new StreamReader("mytext.txt")){Console.WriteLine(sr.ReadToEnd());string line = "";while ((line = sr.ReadLine()) != null){Console.WriteLine(line);}//    //char[] buffer;//    //buffer =new char[(int)sr.BaseStream.Length];//    //sr.Read(buffer, 0, (int)sr.BaseStream.Length);//    //Console.WriteLine(new string(buffer));}//文本复制到另一个文件里char[] buffer;using (StreamReader sr = new StreamReader("mytext.txt")){Encoding en = sr.CurrentEncoding;using (StreamWriter sw = new StreamWriter("mytextto.txt")){//char[] buffer;//int count=(int)sr.BaseStream.Length;//buffer = new char[count];//sr.Read(buffer, 0, count);//Task.Run(()=>sw.WriteAsync(buffer, 0, count));Encoding enw = sw.Encoding;buffer = new char[20];while (true){int r = sr.Read(buffer, 0, 20);if (r == 0) break;sw.Write(buffer, 0, 20);}}}}

 {using (TextWriter tw = new StreamWriter("mytext.txt", false)){tw.Write("sssssssssssss");//tw.Flush();tw.Write("ddddddddddd");//不换行tw.Write(tw.NewLine);//换行符//tw.Flush();tw.WriteLine("cccccccccccccc");//写入，换行tw.WriteLine("eeeeeeeeeeeee");//Task t = tw.WriteAsync("ffffffffff");tw.Flush();//清理缓冲区，把缓冲区的数据写入基础 设备tw.Close();}}

 private void button2_Click(object sender, EventArgs e){//using(FileStream fs=new FileStream("mytext.txt",FileMode.Open,FileAccess.Read))//{//    using(FileStream fs1=new FileStream("mytextto.txt",FileMode.OpenOrCreate,FileAccess.Write))//Append  FileAccess.Write//    {//        byte[] buffer = new byte[1024*1024*5];//        while(true)//        {//           int r = fs.Read(buffer, 0, buffer.Length);//           if (r > 0)//               fs1.Write(buffer, 0, r);//           if (r < buffer.Length) break;//        }//    }//}using (FileStream fs = new FileStream("第一节DataSet与DataTable1.exe", FileMode.Open, FileAccess.Read)){using (FileStream fs1 = new FileStream("D:/第一节DataSet与DataTable2.exe", FileMode.OpenOrCreate, FileAccess.Write))//Append  FileAccess.Write{byte[] buffer = new byte[1024 * 1024 * 5];while (true){int r = fs.Read(buffer, 0, buffer.Length);if (r > 0)fs1.Write(buffer, 0, r);if (r < buffer.Length) break;}}}}

private FileStream readFs;private FileStream writeFs;private int busize = 1024 * 1024 * 5;private byte[] buffer;

 private void button4_Click(object sender, EventArgs e){buffer = new byte[busize];ReadFileAsync("第一节DataSet与DataTable1.exe");}

 private void ReadFileAsync(string fName){readFs = new FileStream(fName, FileMode.Open, FileAccess.Read, FileShare.Read, busize, true);IAsyncResult iResult = readFs.BeginRead(buffer, 0, buffer.Length, OnCompleteRead, null);}object lockbu = new object();

 private void OnCompleteRead(IAsyncResult iResult){int byteCount = readFs.EndRead(iResult);if (byteCount > 0){//写读取到的长度WriteFileAsync("D:/第一节DataSet与DataTable2.exe", byteCount);if (byteCount < busize)readFs.Close();elsereadFs.BeginRead(buffer, 0, busize, OnCompleteRead, null);}elsereadFs.Close();}

 private void WriteFileAsync(string fName, int count){writeFs = new FileStream(fName, FileMode.Append, FileAccess.Write, FileShare.None, count, true);writeFs.BeginWrite(buffer, 0, count, OnCompleteWrite, null);writeFs.Close();}

 private void OnCompleteWrite(IAsyncResult iResult){writeFs.EndWrite(iResult);}