Simple!. Why do we have public library? Because once a book is written, many people can subscribe to it, and re-use it again and again. Right?
In the same way once you create your own class libraries which have multiple functions and procedures, they can be published for your own use, as well as others rewriting or performing copying of the code!
There are other reasons too, but this is a great starting point to know why class library.
Hope it helps.
Best Regards, Dilip

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Class Library is a library of classes, interfaces, and value types that are included in the Windows Software Development Kit (SDK). We can also create your own classes, function procedure and other and all this help to inherit the function from one class to another.

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The greatest benefits are primarily for application extensibility, code re-usability, and program stability. With good programming, a well coded class library can add fantasticintegrityto an application.
But you should also know that the benefitvalue is only going to be as high as the guidelines used by the programmer(s) when developed!
If the classes are not cataloged appropriately within common namespaces or written expressively with explicit naming conventions that have single purpose and high cohesion, then the benefits will be less obvious. And that translated into dollars could mean that the application could be very expensive on theback-end during support andmaintenance.
So when you talk about the benefits, you should also consider craftsmanship to cost, as well asfunctionality.
Cheers!!!
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