Plugin Backward compatibility

I have created one plugin based application, by using MEF. So i have created one interface library which will be implemented by plugins.

But i have one question about backward compatibility,

As i have defined interfaces in PluginInterface library, now if made any change to IPlugin then, i can't load older versions Plugin (which implements older interface) .

So how can i achieve backward compatibility in application?

Please give me suggestions, 开发者_JAVA百科

Thanks

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In order to stay compatable with previous versions you cannot change the interface. If you want to change your interface you need to introduce another new interface (IPlugin2 for example).