using System;
using System.Collections.Generic;
class Program
{
static void Main() {
var list = new List<string> { "c++", "c#", null, "c", null, "java", "php", null };
Console.WriteLine(string.Join(',', list));
list.RemoveAll(item => item == null);
Console.WriteLine(string.Join(',', list));
}
}
/*
run:
c++,c#,,c,,java,php,
c++,c#,c,java,php
*/