thank for time,so
at few place i see that private constructors in class, arrest
1) create instances of the class
2) for other class to derive from the class
i can't see logic for the second point
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microsoft -c# language specifications-page 215
When a class declares only private constructors it is not possible for other classes to derive from the
class or create instances of the class (an exception being classes nested within the class). Private
constructors are commonly used in classes that contain only static members. For example:
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