Overrides of Method() should call base.Method()

Rule ND1204 Object Oriented Design

Overrides should refine or complete the base method behavior; not calling the base method replaces it instead. Violations signal a design flaw, especially when the design justifies replacing rather than refining.

How to fix

Investigate whether inheritance is the right choice, or whether exposing the method polymorphically through an interface would be better. The template method pattern http://en.wikipedia.org/wiki/Template_method_pattern might help.

CQLinq source

This rule is written in CQLinq, C# LINQ over the NDepend code model. It ships with every new NDepend project: you can read it, adapt it, or use it as a starting point for your own custom rules.

// <Name>Overrides of Method() should call base.Method()</Name>
// <Id>ND1204:OverridesOfMethodShouldCallBaseMethod</Id>
warnif count > 0
from t in Types  // Take account of third-party base classes also

// Bother only classes with descendant
where t.IsClass && t.NbChildren > 0

from mBase in t.InstanceMethods
where  mBase.IsVirtual &&
      !mBase.IsThirdParty &&
      !mBase.IsAbstract && 
      !mBase.IsExplicitInterfaceImpl &&
      !mBase.IsPropertyGetter &&
      !mBase.IsPropertySetter &&
      !mBase.IsIndexerGetter &&
      !mBase.IsIndexerSetter &&      
      // Don't take account of virtual methods of the Object type.
      !mBase.Name.EqualsAny("Equals(Object)","ToString()", "GetHashCode()","Finalize()") &&
       mBase.NbLinesOfCode >= 5  && // Need a sufficient behavior to refine
       JustMyCode.Contains(mBase)

from mOverride in mBase.OverridesDirectDerived
where !mOverride.IsUsing(mBase) &&
       JustMyCode.Contains(mOverride)  // Don't warn on generated code
select new { 
   mOverride, 
   shouldCall = mBase, 
   definedInBaseClass = mBase.ParentType,

   Debt = 10.ToMinutes().ToDebt(),
   Severity = Severity.Medium
}

//<Expl>
// The *override {0}* might need to invoke the base method it overrides to *refine* its base behavior.
//</Expl>

//<Desc>
// Overrides should **refine** or **complete** the base method behavior; not
// calling the base method *replaces* it instead. Violations signal a *design
// flaw*, especially when the design justifies replacing rather than refining.
//</Desc>

//<HowToFix>
// Investigate whether *inheritance* is the right choice, or whether exposing
// the method polymorphically through an interface would be better. The
// **template method** pattern
// http://en.wikipedia.org/wiki/Template_method_pattern might help.
//</HowToFix>

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