Productive Rage

2 May 2011

Check, check it out

Just a quickie since I've not got anything particularly new or unique today, just something I came across that was convenient for some code I was writing that I thought I'd share!

I was looking up online the correct pattern for the "Double-Checked Locking Pattern" since I was looking into writing something that would use lazy evaluation while being type-safe (note: its application was probably overkill, but it's fun to look into these things!). I've used it before and generally use it along these lines (after much research one bored afternoon).

public class ExpensiveDataRetriever
{
    private volatile ExpensiveToGenerateDataType _data;
    private object _lock;
    public ExpensiveDataRetriever()
    {
        _data = null;
        _lock = new object();
    }
    public ExpensiveToGenerateDataType Get()
    {
        if (_data == null)
        {
            lock (_lock)
            {
                if (_data == null)
                    _data = doWorkToGenerateData();
            }
        }
        return _data;
    }
    private ExpensiveToGenerateDataType doWorkToGenerateData()
    {
        throw new NotImplementedException();
    }
}

But now .Net 4.0 has an easier solution! I suppose I shouldn't be all that surprised since 4.0 has brought solutions for a lot of threading "stuff" but I hadn't heard of this particular one. The above can be re-written as the below, which I think is a lot clearer.

public class ExpensiveDataRetriever
{
    private Lazy<ExpensiveToGenerateDataType> _data;
    public ExpensiveDataRetriever()
    {
        _data = new Lazy<ExpensiveToGenerateDataType>(doWorkToGenerateData, true);
    }
    public ExpensiveToGenerateDataType Get()
    {
        return _data.Value;
    }
    private ExpensiveToGenerateDataType doWorkToGenerateData()
    {
        throw new NotImplementedException();
    }
}

I read about it at http://csharpindepth.com/Articles/General/Singleton.aspx which - if I'm not mistaken - is where I got the original locking pattern from (though from an older version of the article).

And - oh yes, that article title is a terrible pun on "Double-Checked" vs Beastie Boys. You know you love it :)

Posted at 21:24