Closing streams, always necessary? .net

Is it always necessary to close streams or, because .net is managed code, will it be closed automatically as soon as it drops out of scope (assuming there are no exceptions raised).

Illustrated:

static string SerialiseObjectToBase64(object obj)
{
    var mstream = new MemoryStream();
    ...
    re开发者_JS百科turn Convert.ToBase64String(mstream.ToArray());        
}

Is the above code acceptable?

With a MemoryStream it is a bit of a moot point - since you are ultimately talking to a managed byte[] (so it is still going to wait for routine garbage collection). But in general, yes: you should close (better: Dispose() via using, so it gets shut down upon exception) the stream when done, otherwise you might not flush some data to the underlying (unmanaged) destination. And there are some streams that don't actually fully "flush" on Flush() - they need to be Close()d (compression streams in particular).

It is good practice to close your streams. Use the using statement, and Dispose() will be called when it falls out of scope (or if an exception is thrown), which will in turn close your stream.

static string SerialiseObjectToBase64(object obj)
{
    using (var mstream = new MemoryStream())
    {
        ...
        return Convert.ToBase64String(mstream.ToArray());
    } 
}

Closing streams and disposing of objects are 2 different things. Closing streams flushes the write buffer and writes any unwritten data to the stream. Disposing of the stream will simply release the memory used by the stream variable.

.Net's GC is very... lazy. Just because a reference has been lost doesn't mean it's immediately swept up, crushed and sent to the landfill. It's always a good idea to close open resources and to dispose of objects that implement IDisposable for that very reason.