C# Loop MCQs

Question 6: What will be the output of the following program?

static void Main()
{
    foreach (int number in GetNumbers())
    {
        Console.Write(number.ToString() + " ");
    }
}

public static System.Collections.IEnumerable GetNumbers()
{
    yield return 10;
    yield return 20;
    yield return 30;
}

Answer: B

Here, the first iteration of the foreach loop in the Main() method executes the GetNumbers() method until the first yield return statement is reached. This iteration returns 10, and the current location in the iterator method is retained. On the next iteration, execution in the iterator method continues from where it left off, again stopping when it reaches a yield return statement. This iteration returns 20, and the current location in the iterator method is again retained. The loop completes when the end of the iterator method is reached.

Learn more about iterators.

Question 7: What will be the output of the following program?

static void Main()
{
    foreach (int number in GetNumbers())
    {
        // do nothing
    }
}

public static System.Collections.IEnumerable GetNumbers()
{
    Console.Write("yield-1 ");
    yield return 10;

    Console.Write("yield-2 ");
    yield return 20;

    Console.Write("yield-3");
    yield return 30;
}

Answer: D

Here, the first iteration of a foreach loop in the Main() method executes the GetNumbers() method until the first yield return statement is reached. This iteration prints "yield-1" and returns 10, and the current location in the iterator method is retained. On the next iteration, execution in the iterator method continues from where it left off, again stopping when it reaches a yield return statement. This iteration prints "yield-2" and returns 20, and the current location in the iterator method is again retained. The loop completes when the end of the iterator method is reached.

Learn more about iterators.