What types of collections or data structures are suitable for iteration using the foreach operator?

In C#, the foreach operator can be used to iterate over any collections or data structures that implement the IEnumerable or IEnumerable<T> interface.

Suitable collections:

• Arrays (int[], string[], etc.)
• Lists (List<T>)
• Sets (HashSet<T>)
• Dictionaries (Dictionary<TKey, TValue>) — iterates over key-value pairs
• Queues (Queue<T>), stacks (Stack<T>)
• Any custom collections implementing IEnumerable

Example:

List<string> names = new List<string> { "Anna", "Bob", "Charlie" };

foreach (var name in names)
{
    Console.WriteLine(name);
}

Thus, foreach works with any iterable objects, making it versatile for traversing collections.