Question about updating particles in an arraylist

Basically I made a particle class and emitter class I added them to the list but I was trying to update from each call.

Void Update() {

    if (arraylist1.Count < maxNumberOfParticles)
     {
         //Adds to list
         arraylist1.Add(particle1);
         //Make sphere gameobject
         
     } 
     while (i<arraylist1.Count)
     {
       trying to Update each particle in the array, This is in my emitter class
       //arraylist1[i].Update();  <-- Error here
        i++;
      }

}