`HashSet`

This is an optimized set collection. With HashSet we use the constructor to convert a String array into a set. It can eliminate duplicates from a collection in a VB.NET program.

We can do similar things with HashSet that we can do with Dictionary. The main difference is that Dictionary provides values, and HashSet does not.

Example

We declare a String array of 6 Strings—3 of these strings are equal. Next, we create a HashSet using the generics syntax in the VB.NET language.

And The argument to the HashSet New function is an IEnumerable(Of String). This becomes the contents of the HashSet.

Note Recall that the String array implements the IEnumerable interface, which means it can be used by any method that handles IEnumerable.

Finally We convert back into a String array: all the duplicate Strings were removed.

Module Module1
    Sub Main()
        ' String array.
        Dim a As String() = {"cat", "dog", "cat", "leopard", "tiger", "cat"}
        Console.WriteLine(String.Join(" ", a))

        ' Create HashSet.
        Dim hash As HashSet(Of String) = New HashSet(Of String)(a)

        ' String array.
        a = hash.ToArray()
        Console.WriteLine(String.Join(" ", a))
    End Sub
End Modulecat dog cat leopard tiger cat
cat dog leopard tiger

`Join`

The program uses the String.Join Shared function. With String.Join, you can convert an array into a String. This makes the program require fewer lines.

With the HashSet collection type, you can collapse duplicate elements of an array. We showed String arrays here. But this approach works with other types as well.