//stream 轉為byte[] 
public byte[] stream2byte(Stream stream)
{
    byte[]  buffer= new byte[stream.length];
    stream.Read(buffer,0,buffer.length);
    return buffer;
}
//byte[] 轉stream
public stream byte2stream(byte[] buffer)
{
    stream stream= new MemoryStream(buffer);
    stream.Seek(0,SeekOrigin.Begin);
    //設定stream的position為流的開始
 

    return stream;
}

//stream寫到檔案
public void stream2File(Stream stream)
{
    byte[] buffer= new buffer[stream.length];
    stream.Read(buffer,0,buffer.length);
    FileStream fs= new FileStream(filename,FileMode.Create);
    BinaryWriter writer= new BinaryWriter(fs);
    writer.Writer(buffer);
    writer.Close();
    fs.Close();
}
//讀取檔案到stream
 

public Stream file2Stream(string path)
{
    FileStream fs = new FileStream(path,fileMode.Open,FileAccess.Read);
    byte[] buffer= new byte[fs.length];
fs.Read(buffer,0,buffer.length);
Stream  stream=MemoryStream(buffer);
 stream.Seek(0,seekOrigin.Begin);
return stream;  
}