Why does my attempt to trim strings in a List<string> not appear to work?

List<string> listFromSplit = new List<string>("a, b".Split(",".ToCharArray())).Dump();
listFromSplit.ForEach(delegate(string s)
{
  s.Trim();
});
listFromSplit.Dump();

s = s.Trim();

List<string> temp = new List<string>("a, b".Split(",".ToCharArray()));
List<string> listFromSplit = new List<string>();

temp.ForEach(delegate(string s)
{
    listFromSplit.Add(s.Trim());
});

listFromSplit.Dump();

string[] temp = "a, b".Split(",".ToCharArray());
List<string> listFromSplit = new List<string>();

foreach (string s in temp)
{
    listFromSplit.Add(s.Trim());
};

listFromSplit.Dump();

var s = "  asd   ";
s.Trim();

var s = "   asd   ";
s = s.Trim();

var listFromSplit = "a, b".Split(',').Select(s=>s.Trim());

var result = listFromSplit.Select(s => s.Trim());

var result = from each in listFromSplit select each.Trim();

List<string> listFromSplit =
     new List<string>( "a , b ".Split( new char[] { ',', ' ' }, StringSplitOptions.RemoveEmptyEntries ));