How to delete identical lines in a file, while leaving one of them?

Question

C++ / C#

How to delete identical lines in a file, while leaving one of them? Thanks in advance

Answer 1

var lines = File.ReadAllLines(pathToFile);
var disctinctLines = lines.Distinct();
File.WriteAllLines(pathToFile, disctinctLines);

Works for files that fit in memory.

Answer 2

Dictionary