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

I tried the following code in LINQPad and got the results given below:

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

"a" and " b"

so the letter b didn't get the white-space removed as I was expecting...?

Anyone have any ideas

[NOTE: the .Dump() method is an extension menthod in LINQPad that prints out the contents of any object in a nice intelligently formatted way]

From stackoverflow rohancragg

• you're just creating a trimmed string, not assigning anything to it.

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

  won't update s, while..

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

  will..

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

  would, i suppose, be how i'd go about it.

  From Sciolist

• You are not assigning the trimmed result to anything. This is a classic error, I've only just got out of the habit of making this mistake with string.Replace :)

  From pezi_pink_squirrel

• The string instances are immutable. Anything that seems to modify one, creates a new instance instead.

  From Pablo Marambio

• The String.Trim() method returns a string representing the updated string. It does not update the string object itself, but rather creates a new one.

  You could do this:

  s = s.Trim();
  

  However you cannot update a collection while enumerating through it so you'd want to either fill a new List while enumerating over the existing one or populate the List manually using the string array returned by String.Split.

  Filling a new list:

  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();
  

  Populating Manually:

  string[] temp = "a, b".Split(",".ToCharArray());
  List<string> listFromSplit = new List<string>();
  
  foreach (string s in temp)
  {
      listFromSplit.Add(s.Trim()); 
  };
  
  listFromSplit.Dump();
  

  From akmad

• Split on both spaces and commas and remove any empty entries. All nice and trimmed. Assumes that your strings don't contain spaces, though.

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

  From tvanfosson

• I have no IDE up and running, but this should get the job done (unless I am wrong):

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

  From Adrian

• Further to the answer posted by Adrian Kuhn you could do the following:

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

  From mezoid