Microsoft Certified Solutions Developer (MCSD) Certification Practice Test

What does contravariance allow in the context of delegates?

1. Return types to be less derived than specified

2. Parameter types to be less derived than those specified in the delegate

3. Handling exceptions between different delegates

4. Combining multiple delegates into one

The correct answer is: Parameter types to be less derived than those specified in the delegate

Contravariance in the context of delegates refers to the ability to use a less derived type than originally specified for the parameter types in a delegate. This concept is particularly useful in situations where you want to create a method that can accept arguments of a base class type while the delegate is defined with a derived class type. For instance, if you have a delegate that expects a parameter of a class type (let’s say `Animal`), you can assign a method to that delegate that takes a parameter of a more generic type (like `Mammal`, which is a base class of `Dog`). This flexibility allows for greater reusability and can enhance polymorphism within your code. In contrast, the other options do not correctly represent the notion of contravariance. Return types being less derived is a feature of covariance, not contravariance. Handling exceptions is not specifically related to the concepts of variance in delegates. Lastly, combining multiple delegates is more about multicast delegates and does not pertain to the variance mechanics. Understanding contravariance helps in writing more adaptable code that enhances type compatibility in delegate usage.