/// <summary>
/// 将 Stream 转成 byte[]
/// </summary>
public byte[] StreamToBytes(Stream stream)
{
byte[] bytes = new byte[stream.Length];
stream.Read(bytes, 0, bytes.Length);
// 设置当前流的位置为流的开始
stream.Seek(0, SeekOrigin.Begin);
return bytes;
}
/// <summary>
/// 将 byte[] 转成 Stream
/// </summary>
public Stream BytesToStream(byte[] bytes)
{
Stream stream = new MemoryStream(bytes);
return stream;
}

/* - - - - - - - - - - - - - - - - - - - - - - - -
* Stream 和 文件之间的转换
* - - - - - - - - - - - - - - - - - - - - - - - */
/// <summary>
/// 将 Stream 写入文件
/// </summary>
public void StreamToFile(Stream stream,string fileName)
{
// 把 Stream 转换成 byte[]
byte[] bytes = new byte[stream.Length];
stream.Read(bytes, 0, bytes.Length);
// 设置当前流的位置为流的开始
stream.Seek(0, SeekOrigin.Begin);
// 把 byte[] 写入文件
FileStream fs = new FileStream(fileName, FileMode.Create);
BinaryWriter bw = new BinaryWriter(fs);
bw.Write(bytes);
bw.Close();
fs.Close();
}
/// <summary>
/// 从文件读取 Stream
/// </summary>
public Stream FileToStream(string fileName)
{
// 打开文件
FileStream fileStream = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read);
// 读取文件的 byte[]
byte[] bytes = new byte[fileStream.Length];
fileStream.Read(bytes, 0, bytes.Length);
fileStream.Close();
// 把 byte[] 转换成 Stream
Stream stream = new MemoryStream(bytes);
return stream;
}
详细出处参考：http://www.jb51.net/article/13706.htm