FileStream fs = new FileStream(@"D:\12.txt", FileMode.Open);             byte[] buffer = new byte[1024 * 1024];             fs.Read(buffer, 0, buffer.Length);             string content = Encoding.Default.GetString(buffer);             textBox1.Text = content;             fs.Dispose();

 SaveFileDialog sfd = new SaveFileDialog();             DialogResult rst = sfd.ShowDialog();             if(rst==System.Windows.Forms.DialogResult.OK)             {                 FileStream fs = new FileStream(sfd.FileName,FileMode.Create);                 string content = textBox1.Text;                 byte[] buffer = ASCIIEncoding.UTF8.GetBytes(content);                 fs.Write(buffer,0,buffer.Length);                 fs.Dispose();

FileStream streamread = new FileStream(@"D:\123.wmv",FileMode.Open);             FileStream streamwrite = new FileStream(@"F:\1212.wmv",FileMode.Create);             byte[]buffer=new byte[1024*1024*3];             int Length;             do             {                 Length = streamread.Read(buffer,0, buffer.Length);                 streamwrite.Write(buffer,0, Length);             }             while (Length == buffer.Length);             streamread.Dispose();             streamwrite.Dispose();             MessageBox.Show("Copy Success");