This Function show you how to use Distinct to remove duplicate elements from List.

public void DistinctExample()
{

int[] arr = { 1,2,3,4,2,1,3,5,4,6,4,2,1,9 };

var uniqueValue = arr.Distinct();

Console.WriteLine("Unqieuw Values :");
foreach (var x in uniqueValue)
{
Console.WriteLine(x);
}

}