StackOverflow2013

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POInsertion of classes in the inheritance tree
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copied!<p>I wonder if it would be possible to insert classes in an inheritance tree at arbitrary positions.</p> <p>Example:</p> <pre><code>class Base { public virtual void DoSomething() { Console.WriteLine("Base"); } } class D1:Base { public override void DoSomething() { base.DoSomething(); Console.WriteLine("D1"); } } class D2:Base { public override void DoSomething() { base.DoSomething(); Console.WriteLine("D2"); } } class D3:Base { public override void DoSomething() { base.DoSomething(); Console.WriteLine("D3"); } } </code></pre> <p>Imagine the above classes are from a library with no source available. If I want to modify the behaviour of all the derived classes I have to inherit from all of them and implement the same thing multiple times. Then I have to change all types to my newly derived one. An easier way would be to insert a class directly after Base and somehow (that is probably a big somehow) make the derived class point to that as their base object. The derived classes could then be used unchanged.</p> <pre><code>class Inserted : after Base { public override void DoSomething() { base.DoSomething(); Console.WriteLine("Inserted"); } } </code></pre> <p>or</p> <pre><code>class Inserted : before D1 { public override void DoSomething() { base.DoSomething(); Console.WriteLine("Inserted"); } } </code></pre> <p>The keywords "before" and "after" would control where exactly the class is to be inserted.</p> <p>In the past I worked with a system that would support something like this and it was a huge productivity boost.</p> <p>Is this principially possible with for instance, the .Net CLR or with the Java Runtime? Would it be possible to change the v_table to point to the new base class? Why does no modern system support this? What would the ramifications be regarding reliability, security and so on?</p>

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