c# check textbox for unique values

Question

I have a textbox where user inputs values, each one in a new row, now i want to check if those input values are unique, but looks like it does not work if duplicated value is a last value, don't know why. Any tips? Lets say it is:

1
2
3
3

It will not work, but

1
2
3
3
5

Will work and show an error as duplicate

Here is a code i use: First I split textbox into array of strings

     string[] linesValues = textBoxValues.Text.Split(new Char[] { '\n' }, StringSplitOptions.RemoveEmptyEntries);

then check for duplicates and show error

if (linesValues.Distinct().Count() != linesValues.Count()) { MessageBox.Show("Question values must be unique!", "Duplicated values found", MessageBoxButtons.OK, MessageBoxIcon.Error); return; }

Answer 1

I suggest processing the values: removing empty / all whitespaces strings, leading and trailing spaces at least (note, that "3 " != " 3" != "3"):

1. new Char[] { '\n', '\r' } note \r can appear as a new line; let's be on the safer side of the road
2. .Where(item => !string.IsNullOrWhiteSpace(item)) we don't want all whitespaces line (empty lines included) like " "
3. item => item.Trim() questions processing; let "3" be equal to "3 "

Code:

string[] linesValues = textBoxValues
  .Text
  .Split(new Char[] { '\n', '\r' }, StringSplitOptions.RemoveEmptyEntries) 
  .Where(item => !string.IsNullOrWhiteSpace(item))
  .Select(item => item.Trim())
  .ToArray();

and then check as you do

using System.Linq;

...

if (linesValues.Distinct().Count() != linesValues.Count()) { 
  MessageBox.Show("Question values must be unique!", 
                  "Duplicated values found", 
                   MessageBoxButtons.OK, 
                   MessageBoxIcon.Error); 

  return; 
}