Anonymous Methods / Lambda's (Coding Standards

Question

In Jeffrey Richter's "CLR via C#" (the .net 2.0 edtion page, 353) he says that as a self-discipline, he never makes anonymous functions longer than 3 lines of code in length. He cites mostly readability / understandability as his reasons. This suites me fine, because I already had a self-discipline of using no more than 5 lines for an anonymous method.

But how does that "coding standard" advice stack against lambda's? At face value, I'd treat them the same - keeping a lambda equally as short. But how do others feel about this? In particular, when lambda's are being used where (arguably) they shine brightest - when used in LINQ statements - is there genuine cause to abandon that self-discipline / coding standard?

Answer 1

I don't know if having a guideline for short lambda's and delegates is really useful. However, have a guideline for having short functions. The methods I write are on average 6 or 7 lines long. Functions should hardly ever be 20 lines long. You should create the most readable code and if you follow Robert Martin's or Steve McConnell's advice, they tell you to keep functions short and also keep the inner part of loops as short of possible, favorably just a single method call.

So you shouldn't write a for loop as follows:

for (int i = 0; i < 100; i++)
{
    // Potentially significant amounts of code
}

but simply with a single method call inside the loop:

for (int i = 0; i < 100; i++)
{
    WellDescribedOperationOnElementI(i);
}

With this in mind, while I in general agree with Jon Skeet’s answer, I don't see any reason why you shouldn't want his example to be written as:

Parallel.For(0, 100, i =>
{
    WellDescribedPartOfHeavyCalculation(i);
});

or

Parallel.For(0, 100, i => WellDescribedPartOfHeavyCalculation(i));

or even:

Parallel.For(0, 100, WellDescribedPartOfHeavyCalculation);

Always go for the most readable code, and many times this means: short anonymous methods, and short lambda's, but most of all short -but well described- methods.

Answer 2

Bear in mind that things have changed a lot since 2.0. For example, consider .NET 4's Parallel Extensions, which use delegates heavily. You might have:

Parallel.For(0, 100, i => 
{
    // Potentially significant amounts of code
});

To me it doesn't matter whether this is a lambda expression or an anonymous method - it's not really being used in the same way that delegates typically were in .NET 2.0.

Within normal LINQ, I don't typically find myself using large lambda expressions - certainly not in terms of the number of statements. Sometimes a particular single expression will be quite long in terms of lines because it's projecting a number of properties; the alternative is having huge lines!

In fact, LINQ tends to favour single-expression lambda expressions (which don't even have braces). I'd be fairly surprised to see a good use of LINQ which had a lambda expression with 5 statements in.