Question

After upgrading to ReSharper5 it gives me even more useful tips on code improvements. One I see everywhere now is a tip to replace foreach-statements with LINQ queries. Take this example:

private Ninja FindNinjaById(int ninjaId)
{
    foreach (var ninja in Ninjas)
    {
        if (ninja.Id == ninjaId)
            return ninja;
    }
    return null;
}

This is suggested replaced with the following using LINQ:

private Ninja FindNinjaById(int ninjaId)
{
    return Ninjas.FirstOrDefault(ninja => ninja.Id == ninjaId);
}

This looks all fine, and I’m sure it’s no problem regarding performance to replace this one foreach. But is it something I should do in general? Or might I run into performance problems with all these LINQ queries everywhere?

Answer 1

You need to understand what the LINQ query is going to do “under the hood” and compare that to running your code before you can know whether you should change it. Generally, I don’t mean that you need to know the exact code that will be generated, but you do need to know the basic idea of how it would go about performing the operation. In your example, I would surmise that LINQ would basically work about the same as your code and because the LINQ statement is more compact and descriptive, I would prefer it. There are times, though, when LINQ may not be the ideal choice, though probably not many. Generally I would think that just about any looping construct would be replaceable by an equivalent LINQ construct.