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I like the concept of System.Tuple in that it allows me to return multiple parameters in a single function call without instantiating a new class, however does this defy any good programming practices such as Microsoft Patterns & Practices, SOLID Principles, etc.

I'm just trying to gauge how liberally I should use this feature or if I should only use it in edge case scenarios when necessary.

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+1: Excellent question. Also - I wonder if Anders Hejlsberg has weighed in on this. – Jim G. Dec 8 '11 at 20:06
up vote 8 down vote accepted

The issue with using Tuple is that the generic type parameters do not convey meaning.

For readability you may want to consider using a custom class or even an anonymous type with named members.

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What about the XML parameter description? Not the most obvious place to look, but better than nothing. – John Bubriski Dec 8 '11 at 20:36
@SkippyFire - How do you mean? All you get is the type of T1, T2 etc. Doesn't tell you what they mean. – Oded Dec 8 '11 at 21:00
I have to say: every time I (or someone on our team) has used a Tuple as a type, I am constantly referring back to other parts in the code to remember what .Item1, .Item2, etc. are. For anything that is not completely trivial, create discrete classes. Give yourself a chance in the future to know what it is you were doing. – Joe Dec 9 '11 at 1:29
@Oded I'm talking about adding XML documentation to a method accepting a Tuple. Again, not perfect, but better than nothing if you want/need to use Tuples. – John Bubriski Mar 8 '12 at 18:00
@Oded Also, the parameter or return value may not convey meaning, but the name of the method can. Let's say you have a method called GetTopTwoPercentages() that returns a Tuple<decimal, decimal>. That might be clear enough. – John Bubriski Mar 8 '12 at 18:02

One of the most important code qualities is readability. So ask yourself:
When I (i.e. in anybody else but you) look at the method signature, do I know what meaning the respective components of the Tuple have?
For example if the pair of floats you are returning is a set of polar coordinates, is this clear?

This is clear:

Tuple<Float, Float> getPolarCoords();

This is misleading (because one would assume Cartesian coordinates):

Tuple<Float, Float> getCoords();

And this is devoid meaning:

Tuple<Float, Float> getTuple();

So generally speaking, you will have evaluate clarity on a per-case basis and refactor if necessary. If you represent the same kind of data as Tuple in many different places, then creating a class is definitely a good idea.

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