C# nested stream with using statement, should I use two using?

Question

I'm writing a piece of code which uses nested stream:

using (var zip = new ZlibStream(new MemoryStream(to_be_unziped), CompressionMode.Decompress))
{

}

Is it fine? Or should I write it as:

using (var memory_stream = new MemoryStream(to_be_unziped))
using (var zip = new ZlibStream(memory_stream, CompressionMode.Decompress))
{

}

For readability I use the second one. Technical there is no difference between both versions — Sir Rufo
– Sir Rufo, Commented Jun 11, 2019 at 5:42
There is nothing wrong with the 1st method, but I think 2nd one is more readable but in the second one it should be just memory_stream not var memory_stream — TheLastStark
– TheLastStark, Commented Jun 11, 2019 at 5:42
So in the 1st method, when the outer stream gets closed, the inner one will also be closed, right? — Just a learner
– Just a learner, Commented Jun 11, 2019 at 5:44

halfer · Accepted Answer · 2020-09-12 18:07:15Z

2

When you create a ZlibStream and pass in MemoryStream it holds a reference to it.

When it's Disposed, it calls Close on that reference, which in turn will hit the Dispose plumbing of abstract Stream class.

protected override void Dispose(bool disposing)
{
    try
    {
        if (!_disposed)
        {
            if (disposing && (this._baseStream != null))
                this._baseStream.Close();
            _disposed = true;
        }
     }
     finally
     {
        base.Dispose(disposing);
     }
}

It's worth noting, that a MemoryStream has no unmanaged resources anyway, and actually doesn't need to be Disposed, it doesn't override the Close of the Stream class.

Stream also checks if Dispose has already been called. Meaning in most cases, you only have to Dispose the stream you are working with.

edited Sep 12, 2020 at 18:07

halfer

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answered Jun 11, 2019 at 5:53

TheGeneral

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