Array Split with reference element in c#

arraysplitwithrefelement.cs

//Desc: Array Split
//Say you have an array (or list) of arbitrary integers. 
//The data structure must be reordered so that all values less than a 
//special reference value are placed on the left. All values greater than 
//or equal to the reference value are placed on the right. 
//The ordering within the subranges is not relevant and may vary.

//Input                         Reference element   Sample result
//[4, 7, 1, 20]                     9               [1, 4, 7, 9, 20]
//[3, 5, 2]                         7               [2, 3, 5, 7]
//[2, 14, 10, 1, 11, 12, 3, 4]      7               [2, 1, 3, 4, 7, 14, 10, 11, 12]
//[3, 5, 7, 1, 11, 13, 17, 19]      11              [1, 3, 5, 7, 11, 11, 13, 17, 19]

var lst = new List<int> { 4, 7, 1, 20 };
int refelt = 9;

var lesslst = lst.Where(x => x < refelt).ToList();
lesslst.Add(refelt);
var grtlst = lst.Where(x => x > refelt).ToList();

var res = lesslst.Concat(grtlst).ToList();

res.ForEach(x => Console.WriteLine(x));