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What is the prefered score range for the code metrics calculation for the following

  • Maintainability Index
  • Cyclomatic Complexity
  • Depth of Inheritance
  • class Coupling
Asad
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2 Answers2

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The theoretically optimal values are:

  • Maintainability index: 100. Higher values indicate better maintainability.
  • Cyclomatic complexity: 1. The number of different paths that code can take.
  • Depth of inheritance: 1. The number of class definitions above this one in the inheritance tree, not including interfaces.
  • Class coupling: 0. Number of other entities this entity is dependent on.

There are no hard and fast "good" ranges, though it's possible to make some general statements.

  • Having high per-method cyclomatic complexity suggests a method is getting too complicated.
  • Having an inheritance depth more than about 3 or 4 (of your own classes, not the framework's) is a trouble sign that you may be unnecessarily representing abstract relationships that aren't really in your software's domain.
  • Low class coupling is in general better, but sometimes it's unavoidable. To the extent possible, you should definitely minimize the dependency between namespaces, since there's much less reason for dependencies here.

A project could only reach all four values simultaneously by essentially doing nothing and being useless: software that does nothing and depends on nothing is certainly maintainable, but not a very good use of client dollars.

Therefore, all complexity is a tradeoff: additional so-called inherent complexity encodes more sophistication into the program, allowing it to expand the feature set. What you would like to avoid is accidental complexity introduced by a poor or deficient implementation.

John Feminella
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    There really are no hard and fast good ranges. Especially if you use something like expression trees, or the new dynamic keyword your class coupling is shot to the moon. – R. Martinho Fernandes Jan 09 '10 at 15:13
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Before relying too heavily on it (or relying on it at all), check the following page, which gives more detail on how the metric is computed:

https://avandeursen.com/2014/08/29/think-twice-before-using-the-maintainability-index/

VS' Maintainability Index is a poorly-validated combination of metrics, which itself relies a metric (cyclomatic complexity) that has been shown to not correlate with code understandability (which would therefore not correlate with maintainability). See "Automatically Assessing Code Understandability: How Far Are We?", by Scalabrino et al. and https://shape-of-code.com/?s=cyclomatic+complexity

Furthermore, the constants and function choices used in this metric have not been calibrated on C# or VB code, which further makes it useless.

(This addresses the original question by pointing out that the original question should not even be asked.)

user3511585
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