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

Ran into the same problem. @Lee already explained that Lamda .ForEach() uses a copy.

You can write an Extension Method like this and use a for loop (foreach also not possible):

public static class StringListExtensions {     public static void TrimAll(this List<string> stringList)     {         for (int i = 0; i < stringList.Count; i++)         {             stringList[i] = stringList[i].Trim(); //warning: do not change this to lambda expression (.ForEach() uses a copy)         }     } } 

Use it like this:

var productNumbers = new List<string>(){ "11111", " 22222 " } productNumbers.TrimAll(); 

should result in: List(){ "11111", "22222" }

I didn't use the split and re-join solution (chosen solution) because there can be a comma inside one of the string items. The regex version is not self explanatory. This is old-school but safer and can be easily understood...