How can I trim all elements in a list?

Question

I'm trying the following

string tl = " aaa, bbb, ccc, dddd             eeeee";

var tags = new List<string>();
tags.AddRange(tl.Split(','));
tags.ForEach(x => x = x.Trim().TrimStart().TrimEnd());

var result = String.Join(",", tags.ToArray());

But it doesn't work, the tags always come back as " aaa", " bbb".

How can I trim all elements in a list?

Answer 1

// you can omit the final ToArray call if you're using .NET 4
var result = string.Join(",", tl.Split(',').Select(s => s.Trim()).ToArray());

If you only need the final result string, rather than the intermediate collection, then you could use a regular expression to tidy the string. You'll need to benchmark to determine whether or not the regex outperforms the split-trim-join technique:

var result = Regex.Replace(tl, @"(?<=^|,) +| +(?=,|$)", "");

Answer 2

Your problem is that there is no comma between dddd and eeeee. If you want those to be separate, you need to split on ' ', strip the commas, and then trim extra whitespace.

string tl = " aaa, bbb, ccc, dddd                eeeee";

var result = t1.Split(' ').Where(s => !String.IsNullOrEmpty())
                          .Select(s => s.Replace(',','').Trim())
                          .ToArray();

Answer 3

The reason your approach doesn't work is that the x is a copy of the current string reference being processed in the ForEach call (i.e. local to the delegate). Therefore the assignment doesn't affect the item referenced in the list.

Answer 4

What's going on is that you're trying to modify a collection using a foreach statement- which is a no-no. Collections cannot be modified with a foreach.

You'll need to modifiy it a for loop, or, using lambdas, you can use LukeH's solution.