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POAre C#'s partial classes bad design?
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copied!<p>I'm wondering why the 'partial class' concept even exists in C#/VB.NET. I'm working on an application and we are reading a (actually very good) book relavant to the development platform we are implementing at work. In the book, the author provides a large code base/wrapper around the platform API and explains how he developed it as he teaches different topics about the platform development.</p> <p>Anyway, long story short - he uses partial classes, all over the place, as a way to fake multiple inheritance in C# (IMO). Why he didn't just split the classes up into multiple ones and use composition is beyond me. He will have 3 'partial class' files to make up his base class, each w/ 3-500 lines of code... And does this several times in his API.</p> <p><strong><em>Do you find this justifiable?</em></strong> If it were me, I'd have followed the S.R.P. and created multiple classes to handle different required behaviors, then created a base class that has instances of these classes as members (e.g. composition). Why did MS even put partial class into the framework? They removed the ability to expand/collapse all code at each scope level in C# (this was allowed in C++) because it was obviously just allowing bad habits - partial class is, IMO, the same thing. <strong><em>I guess my question is: Can you explain to me when there would be a legitimate reason ever to use a partial class?</em></strong> </p> <p><strong><em>EDIT: I'm aware that for Web/WinForms there is no other choice. But outside of this? Why didn't MS just put some different keyword for gluing code-genn'ed classes together? Or is there really a legit design scenario that merits it?</em></strong></p> <p><strong><em>I do not mean this to be a rant / war thread. I'm honestly looking to learn something here. When should partial classes be used in code design? Simple question, no need to close</em></strong></p> <p>Thanks</p>

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