NGWS SDK Documentation  

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4.5 Overridable methods

An Overridable method is a method whose implementation can be changed by derived classes. This enables classes to exhibit polymorphic behavior wherein the actions performed by a method invocation vary depending on the runtime type of the instance through which the method is invoked.

MustOverride methods are a form of overridable method in which the class that introduces the method defines the method name, return type, parameter types, and accessibility level but no implementation of the method is provided. MustOverride methods are allowed only in MustInherit classes.

In contrast to overridable methods, the implementation of a non-overridable method is invariant: the implementation is the same whether the method is invoked on an instance of the class in which it is declared or an instance of a derived class. In a non-overridable method invocation, the compile time type of the instance is the determining factor.