Question

I have read couple of articles on Linq and Func<> and understood simple examples but I cannot able to use them in day to day programming. I am keen to know what are the scenarios the LINQ or lambda expressions useful and should be used

For this code: Can I use Linq or lambda expressions

List<int> abundantNumbers = new List<int>();
for (int i = 0; i < 28888; i++)
     {
      if (i < pta.SumOfDivisors(i))
         {
          abundantNumbers.Add(i);
          }
     }

Answer 1

Yes, you can absolutely use LINQ in your example:

var abundantNumbers = Enumerable.Range(0, 28888)
                                .Where(i => i < pta.SumOfDivisors(i))
                                .ToList();

Note that it’s important that you didn’t just post code which added to list – you posted code which showed that the list was empty to start with. In other words, you’re creating a list. If you’d merely had code which added to an existing list, I’d have used something like:

var query = Enumerable.Range(0, 28888).Where(i => i < pta.SumOfDivisors(i));
abundantNumbers.AddRange(query);