Question:

What is the output of the program below? Explain your answer.

delegate void Printer();

static void Main()
{
      List<Printer> printers = new List<Printer>();
      for (int i = 0; i < 10; i++)
      {
           printers.Add(delegate { Console.WriteLine(i); });
      }

      foreach (var printer in printers)
      {
           printer();
      }
}

Answer:

This program will output the number 10 ten times.

Here’s why: The delegate is added in the for loop and “reference” (or perhaps “pointer” would be a better choice of words) to i is stored, rather than the value itself. Therefore, after we exit the loop, the variable i has been set to 10, so by the time each delegate is invoked, the value passed to all of them is 10.


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