Using the properties of .NET Enumerations, it is easy to think of ways to repeat elements endlessly.

Infinite sequences in F#

let infiniteZeroes () =
  seq {
    while true do yield 0
  }

Infinite Enumeration in C#

IEnumerable<int> InfiniteZeroes()
{
  while(true)
  {
    yield return 0;  
  } 
}