问题
Should I allocate the memory or just the object of the memory stream: Is this OK?
MemoryStream memoryStream = new MemoryStream();
bitmap.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Jpeg);
If I need to define the MemoryStream size, how can I get it from Bitmap?
回答1:
.NET is a managed environment: specifically, memory allocation is usually managed on your behalf by the .NET runtime. You don't typically need to allocate the memory yourself.
Sometimes, however, you do need to inform the runtime when you've finished with memory by using Close() or Dispose(). The using statement can be used to wrap a resource such as MemoryStream to tell the runtime that the memory can be reclaimed.
回答2:
You don't need to preallocate memory.
You can get the size afterwards with memoryStream.Length.
After you've done what you need to with your memoryStream, be sure to dispose it (or wrap it all in a using statement).
来源：https://stackoverflow.com/questions/8666330/saving-a-bitmap-into-a-memorystream