Microsoft Certified Solutions Developer (MCSD) Certification Practice Test

How can you check if an attribute is applied to a class or method in C#?

1. By using a method from the Attribute class

2. By checking the class inheritance

3. By calling the GetCustomAttribute method

4. By using the yield keyword

The correct answer is: By using a method from the Attribute class

The ability to check if an attribute is applied to a class or method in C# can be effectively achieved by using a method from the Attribute class. Attributes in C# are a powerful way to add metadata to program elements, such as classes and methods. When you define an attribute, you can inspect it at runtime using reflection. One key method from the Attribute class that enables this inspection is `GetCustomAttribute`. This method allows you to query whether a specific attribute type exists on a class or method. You would typically use reflection by calling `GetType().GetCustomAttributes(typeof(YourAttribute), false)`, which will provide an array of attributes applied to the class or method. If the specified attribute is present, you can confirm its application. In contrast, checking class inheritance involves evaluating whether a class derives from another class, which does not directly indicate whether an attribute is applied. The yield keyword is used for iterator methods and is unrelated to attribute application. Thus, the correct choice is one that directly pertains to the functionality offered by reflection and the Attribute class methods for querying applied attributes.