How to determine on which cycle the delay occurs?

Question

C++ / C#

foreach (var i in i2)
{
}

The program reads file properties in a loop. There are a lot of files
On some cycles there are delays
How to determine on which cycle there is a delay?

Answer 1

Logging

Answer 2

??

Logging

profiling! https://msdn.microsoft.com/en-us/library/ms182398.aspx