How to remove duplicates from list C#

Question

I want get same result as got with this code to remove duplicates for text document:

 File.WriteAllLines(@"doc.txt", lines.Select(line1 => line1.Trim()).Distinct().ToArray());

Same for list with large content after loading into the list or on the stage of loading but not from processed file:

List<string> contentList = new List<string>(); 

to read content I use it this way:

for (int i = 0; i < contentList.Count; i++)
{                        
     textBox8.AppendText(contentList[i] + "\n");                        
}

and on the loading stage also inside the loop string by string:

contentList.Add(inputStr);

Desired result is avoid duplicates if I got duplicates inside:

one
two
three
four
two
five
six
three

desired result should be:

one
two
three
four    
five
six

Answer 1

If you have list of strings you can use Distinct() method of LINQ.

var result = contentList.Distinct();

If you have list of objects then you will need to implement custom equality comparer which will lets you to apply custom distinct rule.

Please make sure you included System.Linq namespace.