Codeless: C# Keywords - yield - Iterators without classic iterator code

Oscar Brito

Codeless with c#:
        public static IEnumerable GetThings()
            List<int> col = new List<int>();

            for (int i = 0; i <= 100; i++)

            return col.AsEnumerable();

        public static IEnumerable GetThingsBetter()
            for (int i = 0; i <= 100; i++)
                yield return i;


        public void Yield_Keyword()
            List<int> i1 = new List<int>(GetThings().Cast<int>());
            List<int> i2 = new List<int>(GetThingsBetter().Cast<int>());


From Msdn:

"The yield keyword signals to the compiler that the method in which it appears is an iterator block. The compiler generates a class to implement the behavior that is expressed in the iterator block. In the iterator block, theyield keyword is used together with the return keyword to provide a value to the enumerator object."

Let's see how it can be used:

"The yield statement can only appear inside an iterator block, which can be implemented as the body of a method, operator, or accessor. The body of such methods, operators, or accessors is controlled by the following restrictions:

  • Unsafe blocks are not allowed.

  • Parameters to the method, operator, or accessor cannot be ref or out.

  • A yield return statement cannot be located anywhere inside a try-catch block. It can be located in a try block if the try block is followed by a finally block.

  • A yield break statement may be located in a try block or a catch block but not a finally block."

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