Generic Types and Constraints

Question

Describe generic types and the generic type constraints you know.

Short interview answer

Generics let one type or method work with many types while preserving compile-time type safety. Constraints limit acceptable type arguments, for example class, struct, new(), a base class, an interface, unmanaged, Enum, or Delegate.

Detailed answer

List<T> is a common example: List<int> accepts integers without runtime casts or boxing. Constraints express requirements needed by the implementation. For example, where T : IComparable<T> permits CompareTo, and where T : new() permits new T(). Static fields in a generic class belong to each closed constructed type, so Cache<int> and Cache<string> have separate static state.

Sources

• Microsoft Learn: Generic types and methods