Microsoft Certified Solutions Developer (MCSD) Certification Practice Test

What is the main use of the "dynamic" keyword in C#?

1. To enforce type safety at compile-time

2. To perform static type checking

3. To enable runtime type checking

4. To specify the return type of a method

The correct answer is: To enable runtime type checking

The "dynamic" keyword in C# is primarily used to enable runtime type checking. This means that when you declare a variable as dynamic, the actual type of that variable is determined at runtime instead of at compile-time. This allows developers to work with objects that might not be known until the program is running, providing flexibility when dealing with types that are not statically typed. When using a dynamic type, the compiler does not check for type correctness until the code is executed. This is particularly useful in scenarios such as interoperability with COM objects, working with dynamic languages, or when leveraging data structures like JSON where types might be inconsistent or unknown at compile time. Using dynamic allows for code that can adapt to varying types, greater ease of use with certain data structures, and the ability to bypass the rigid type system of C#. However, using dynamic means losing some compile-time safety, which is why it is important to apply it judiciously in situations where flexibility is necessary.