FileStream fs1 = new FileStream(@"E:\tenp\doc\111.txt", FileMode.Open, FileAccess.Read, FileShare.Read);
FileStream fs2 = new FileStream(@"E:\temp\doc\222.txt", FileMode.Create, FileAccess.Write, FileShare.None);
byte []farr = new byte[1024];
const int rbuffer=1024;
//fs1.ReadByte(); //讀取單個位元組，返回-1表示讀完
while (fs1.Read(farr, 0, rbuffer)!=0) //返回0表示讀完
{
	fs2.Write(farr, 0, rbuffer);
}
fs1.Close();
fs2.Close();
 

讀取與寫入byte[] 

protected void ByteToString_Click(object sender, EventArgs e)
        {


            string content = this.txtContent.Text.ToString();

            if (string.IsNullOrEmpty(content))
            {
                return;
            }

            //string 轉為byte陣列
            byte[] array = Encoding.UTF8.GetBytes(content);

            //將byte陣列轉為string
            string result = Encoding.UTF8.GetString(array);


            Response.Write(result);


        }
        //利用byte[]陣列寫入檔案
        protected void writerFile_Click(object sender, EventArgs e)
        {

            string content = this.txtContent.Text.ToString();

            if (string.IsNullOrEmpty(content))
            {
                return;
            }

            //將string轉為byte陣列
            byte[] array = Encoding.UTF8.GetBytes(content);

            string path = Server.MapPath("/test.txt");
            //建立一個檔案流
            FileStream fs = new FileStream(path, FileMode.Create);

            //將byte陣列寫入檔案中
            fs.Write(array, 0, array.Length);
            //所有流型別都要關閉流，否則會出現記憶體洩露問題
            fs.Close();

            Response.Write("儲存檔案成功");


        }
        //利用byte[]陣列讀取檔案
        protected void readFile_Click(object sender, EventArgs e)
        {
            string path = Server.MapPath("/test.txt");

            FileStream fs = new FileStream(path, FileMode.Open);

            //獲取檔案大小
            long size = fs.Length;

            byte[] array = new byte[size];

            //將檔案讀到byte陣列中
            fs.Read(array, 0, array.Length);

            fs.Close();

            //將byte陣列轉為string
            string result = Encoding.UTF8.GetString(array);


            Response.Write(result);

            

        }