ForEach to Trim string values in string array

Question

I just wondered why this ForEach doesn't work and leaves the values with trailing whitespace.

string days = "Monday, Tuesday, Wednesday, Thursday, Friday";

string[] m_days = days.Split(',');

m_days.ToList().ForEach(d => { d = d.Trim(); } );

I know there are other ways of doing this so i don't need and answer there.

Answer 1

Because you are not reassigning the trimmed strings.

var list = m_days.Split(',').Select(s => s.Trim()).ToList();

Why ForEach doesn't work or if I am using the ForEach incorrectly?

ForEach is not Linq, it's a method of List<T>. What you are doing is basically this:

foreach(string day in m_days)
{
    day.Trim();  // you are throwing away the new string returned by String.Trim
}

Instead of using LINQ you could also use a for-loop instead:

for(int i = 0; i < m_days.Length; i++)
{
    m_days[i] = m_days[i].Trim();
}