warning CS0618: 'UsingEngine.GameObeject.active' is obsolete : 'GameObject.active is obsolete.Use GameObject.SetActive(),GameObject.activeSelf or GameObject.activeInHierarchy.'

Questions & Answers
1

It’s my code and it works fine but always it shows that error,
what should I do ? should I really change it or it’s fine?
because the game works fine.

// pushing Escape= stop the game
//pushing Espace when the game is stopped will resume the game

public GameObject stopimage;

void Update () {		
	if (Input.GetKeyDown (KeyCode.Escape)&& !stopimage.active ) {
		stopimage.SetActive (true);
		Time.timeScale = 0;
	}
	else if (Input.GetKeyDown (KeyCode.Escape)&& stopimage.active) {
		stopimage.SetActive (false);
		Time.timeScale = 1;
	}
}
2

GameObject.activeSelf

returns true if that gameobject is active, false otherwise. Note: It is possible for this to return true, but have the object behave as if it is inactive, due to a parent object being inactive. Documentation.

GameObject.activeInHierarchy

returns true if that object and all parent objects are active, false otherwise. Documentation.

Most of the time, you will want to use activeInHierarchy - it has the same behavior as the old .active

 public GameObject stopimage;
 void Update () {        
     if (Input.GetKeyDown (KeyCode.Escape)&& !stopimage.activeInHierarchy) {
         stopimage.SetActive (true);
         Time.timeScale = 0;
     }
     else if (Input.GetKeyDown (KeyCode.Escape)&& stopimage.activeInHierarchy) {
         stopimage.SetActive (false);
         Time.timeScale = 1;
     }
 }