What are some examples of using HashSet in C#?

Can you give me some examples of using HashSet in C#?

Sure! A HashSet in C# is a collection that contains no duplicate elements. Here's a simple example:

HashSet<int> numbers = new HashSet<int>();

numbers.Add(1);
numbers.Add(2);
numbers.Add(2); // This will not be added

foreach (var number in numbers) {
    Console.WriteLine(number); // Outputs: 1, 2
}

What are the benefits of using HashSet over List?

The main benefits of using HashSet over List include:

1. No Duplicates: HashSet automatically prevents duplicate entries.
2. Faster Lookups: HashSet provides O(1) average time complexity for lookups, while List is O(n).
3. Set Operations: HashSet supports set operations like union, intersection, and difference.

Can you show me how to perform set operations with HashSet?

Absolutely! Here's an example of union and intersection with HashSet:

HashSet<int> setA = new HashSet<int> { 1, 2, 3 };
HashSet<int> setB = new HashSet<int> { 3, 4, 5 };

// Union
setA.UnionWith(setB); // setA now contains 1, 2, 3, 4, 5

// Intersection
HashSet<int> intersection = new HashSet<int>(setA);
intersection.IntersectWith(setB); // intersection contains 3

Are there any performance considerations I should be aware of?

Yes, while HashSet is generally faster for lookups, it can consume more memory than a List due to its underlying data structure. Additionally, if you have a large number of elements with many collisions, performance may degrade. It's important to choose the right collection based on your specific use case.