Why does my attempt to trim strings in a List<string> not appear to work?
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03-07-2019 - |
Question
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]
Solution
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();
OTHER TIPS
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.
Further to the answer posted by Adrian Kuhn you could do the following:
var result = listFromSplit.Select(s => s.Trim());
The string instances are immutable. Anything that seems to modify one, creates a new instance instead.
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 :)
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();
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 ));
The linq options others have provided should work well. As another option, here is an extension method using a for loop:
public static void TrimCollection(this IList<string> stringCollection) {
for (int i = 0; i <= stringCollection.Count() - 1; i++)
stringCollection[i] = stringCollection[i].Trim();
}