Jason Tang | C# - HashSet Common Methods

C# - HashSet Common Methods

HashSet can be use to remove duplicates and union different HashSets. Below are the three basic characteristics that differentiate C# HashSet from other generic and non-generic collections in the .NET framework.

Searching in HashSet<T> is extremely fast because the Contains method of the HashSet<T> collection uses hash-based searching mechanism to find elements.
Duplicate elements cannot be added in a HashSet<T>. Duplicate elements, if added are internally ignored without giving an errors.
Indexed based elements access is allowed in a HashSet<T>.

`HashSet Contains`

// Using contains method. Returns bool; true/false
HashSet<string> countries = new HashSet<string> { "usa", "china", "korea", "german" };

Console.WriteLine(countries.Contains("usa")); // output: true

`HashSet Add`

HashSet<string> countries = new HashSet<string> { "usa", "china", "korea", "german" };

countries.Add("france");

foreach (var country in countries)
{
    Console.WriteLine(country); // usa, china, korea, german, france
}

`HashSet Remove`

HashSet<string> countries = new HashSet<string> { "usa", "china", "korea", "german" };

countries.Remove("china");

foreach (var country in countries)
{
    // output: usa, korea, german
}

`HashSet RemoveWhere`

HashSet<string> countries = new HashSet<string> { "usa", "china", "korea", "german", "japan" };

// needs to use lambda. Only 'german' and 'japan" contains 'an'
countries.RemoveWhere(r => r.Contains("an"));

foreach (var country in countries)
{
    Console.WriteLine(country); // output: usa, china, korea
}

`HashSet UnionWith`

HashSet<string> countries = new HashSet<string> { "usa", "china", "korea", "german" };
HashSet<string> countries1 = new HashSet<string> { "usa", "china", "korea", "japan" };

countries.UnionWith(countries1);

foreach (var country in countries)
{
    Console.WriteLine(country); // output: usa, china, korea, german, japan
}

`HashSet IntersectWith`

HashSet<string> countries = new HashSet<string> { "usa", "china", "korea", "german", "japan" };
HashSet<string> countries1 = new HashSet<string> { "usa", "china", "japan" "Taiwan", "Canada" };

countries.IntersectWith(countries1);

foreach ()
{
    // output: usa, china, japan
}

`HashSet ExceptWith`

HashSet<string> countries = new HashSet<string> { "usa", "china", "korea", "german", "japan" };
HashSet<string> countries = new HashSet<string> { "usa", "china", "korea" };

countries.ExceptWith(countries1);

foreach ()
{
    // output: german, japan
}