Applying Action Delegate

Question

Just to understand the collection ,I tried to find the square of each number passed in to a collection.

My Code is (Ofcourse I could have implemented in differ way,Just to know casting itretaions,I have made a dummy implementation).

   static void Main()
   {
      ICollection<int> Present = (ICollection<int>)
                                  a.GetNumbers(new int[]{1,2,3});

       foreach (int i in Present)
       {
                   Console.WriteLine("{0}", i);
       }
   }


  public IEnumerable<int> GetNumbers(int[] Numbers)
  {
     //first trial
     ICollection<int> col = 
                           Array.ForEach(Numbers, delegate { x => x * x; });

     //second trial
     ICollection<int> col = Array.ForEach(Numbers, ( x => x * x ));

     return (IEnumerable<int>)col.GetEnumerator();

  }

What is the problem with Array.ForEach in bothh trails inside GetNumbers() ?

I am receiving "Assignment and call increment is allowed". error.

Answer 1

Action doesn't return anything, and neither does Array.ForEach - but your lambda expression does, and you're trying to use the result of Array.ForEach despite it being a void method. Try Array.ConvertAll instead, which uses a Converter<TInput, TOutput> (equivalent to Func<TIn, TOut>).

Alternatively, if you want to explore Array.ForEach and Action, do something like:

Array.ForEach(Numbers, x => Console.WriteLine(x * x));

(Also, your first attempt seems to be a mixture of anonymous method syntax and lambda syntax. That won't work.)

Like this:

int[] squares = Array.ConvertAll(numbers, x => x*x);

Answer 2

This is a school book example of where the LINQ extensions methods come in handy, why don't you just do this:

public IEnumerable<int> GetNumbers(IEnumerable<int> numbers)
{
    return numbers.Select(x => x * x);
}