When I first compiled and executed this code segment (excluding the commented statements), it seemed that the loop didn’t wait for 1 millisecond (which usually takes about ten to twenty milliseconds) before executing other code. Because the code I use to do other things depends on waiting for a millisecond (usually ten to twenty milliseconds) on the first iteration of the loop, it resulted in an error. Then, I modified the code slightly (adding the commented statements), and subsequent executions were all normal. Why did this happen?

Here’s the code snippet for reference:

for (int i = 0; i < 10; i++) {
    if (i == 0) {
        //Console.WriteLine(Stopwatch.GetTimestamp());
        Thread.Sleep(1);
    } else {
        Console.ReadLine();
    }
    //Console.WriteLine(Stopwatch.GetTimestamp());
    // Do other things
}