C# Paradigms: Side effects on Lists

Question

I am trying to evolve my understanding of side effects and how they should be controlled and applied.

In the following List of flights, I want to set a property of e

Answer 1

You have two ways of achieving it the LINQ way:

1. explicit foreach loop

   foreach(Flight f in fResults.Where(flight => flight.NonStop))
     f.Description = "Fly Direct!";
   

2. with a ForEach operator, made for the side effects:

   fResults.Where(flight => flight.NonStop)
           .ForEach(flight => flight.Description = "Fly Direct!");
   

The first way is quite heavy for such a simple task, the second way should only be used with very short bodies.

Now, you might ask yourself why there isn't a ForEach operator in the LINQ stack. It's quite simple - LINQ is supposed to be a functional way of expressing query operations, which especially means that none of the operators are supposed to have side effects. The design team decided against adding a ForEach operator to the stack because the only usage is its side effect.

A usual implementation of the ForEach operator would be like this:

public static class EnumerableExtension
{
  public static void ForEach (this IEnumerable source, Action action)
  {
    if(source == null)
      throw new ArgumentNullException("source");

    foreach(T obj in source)
      action(obj);

  }
}