So I finally perfected my RTS multiple movement. The situation is that the game objects are added into a list in a script bound to the camera called UnitController they are added from a unit client script MultiselectClient, this client accesses the UnitController class and adds itself the gameObject into the list. Each time I do the drag select I want it to clear the list first before adding any more. But for some reason, it doesn't work?

This is in my UnitController (below):

void MultiSelect(RaycastHit hit)
{
    Debug.Log(SelectedUnits);
    if (SelectedUnits.Count > 0)
    {
        Debug.Log("Moving group to: " + hit.point);
        foreach(GameObject gameObject in SelectedUnits)
        {
            gameObject.GetComponent<NavMeshAgent>().SetDestination(hit.point);
        }
    }
}

This is in my client (below):

public bool Selected = false;
void Update()
{
    if (Input.GetMouseButton(0))
    {
        Vector3 camPos = Camera.main.WorldToScreenPoint(transform.position);
        camPos.y = Screen.height - camPos.y;

        //if inside the cameras drag selection area then mark player as selected
        Selected = UnitController.selection.Contains(camPos);

        Debug.Log("Selected");
        if(selected){
           addTo();
        }
    }


}

void addTo()
{

    UnitController.SelectedUnits.Remove(gameObject); //I have also tried .clear() which also hasnt worked.



    if (!UnitController.SelectedUnits.Contains(gameObject))
    {
        UnitController.SelectedUnits.Add(gameObject);
        Debug.Log("Added to list: " + UnitController.SelectedUnits);
    }
    else
    {
        Debug.Log("Im already in that list.");
    }
}