How can I make a function run only once and not every frame in C#?

Question

C++ / C#

the function OnTriggerEnter and OnTriggerExit emits values ​​every frame, but how to make it emit values ​​only once

Answer 1

Add a condition.

bool fired = false;

void OnCollisionEnter(Collision col) 
{
   if(!fired)
   {
      // код
      fired = true;
   }
}