您可以使用 MemoryStream.WriteTo 或 Stream.CopyTo(在框架版本 4.5.2 中支持，4.5.1, 4.5, 4) 将内存流的内容写入另一个流的方法.

You may use MemoryStream.WriteTo or Stream.CopyTo (supported in framework version 4.5.2, 4.5.1, 4.5, 4) methods to write content of memory stream to another stream.

memoryStream.WriteTo(fileStream);

更新:

fileStream.CopyTo(memoryStream);
memoryStream.CopyTo(fileStream);