Is it possible to call a function on Unity Program Start?

RuntimeInitializeOnLoadMethodAttribute can help you :)

using UnityEngine; class MyClass { [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)] static void OnBeforeSceneLoadRuntimeMethod() { Debug.Log("Before scene loaded"); } } 

Here you can find the execution order of all functions in unity: http://docs.unity3d.com/Manual/ExecutionOrder.html

Awake is the first function to be executed in your standalone application. For it to run you need to have a GameObject with a attached script containing the Awake function. This should be added to every scene if you want it to run regardless of the scene.

You still have to decide what is the startup scene of your game. So it is enough to add the GameObject there, if you actually want it to run just in the start of the program.

I use a prefab _AppStartup which is just an empty game object having a script AppStartup. Drag this in every scene and configure AppStartup to be executed as first like @maZZZu has stated.

AppStartup performs the following jobs:

• Global initialisation tasks when the app is started
• Switch to boot scene if have start an arbitrary scene in editor mode

• Scene specific initialisation tasks

  public class AppStartup : MonoBehaviour { const int bootSceneNo = 0; public static bool veryFirstCallInApp = true; void Awake () { if (veryFirstCallInApp) { ProgramBegins (); if (Application.loadedLevel != bootSceneNo) { // not the right scene, load boot scene and CU later Application.LoadLevel (bootSceneNo); // return as this scene will be destroyed now return; } else { // boot scene stuff goes here } } else { // stuff that must not be done in very first initialisation but afterwards } InitialiseScene (); veryFirstCallInApp = false; DestroyObject (gameObject); } void ProgramBegins() { // code executed only once when the app is started } void InitialiseScene () { // code to initialise scene } } 

So all you have to do is drag this prefab in every scene manually and give it -100 or whatever in the script execution order. Especially when the project grows and relies on a predefined scene flow it will save you al lot time and hassle.

Yes...

Decorate your method with [RuntimeInitializeOnLoadMethod].

It will be invoked as soon as the scene has finished loading (after Awake events).

[RuntimeInitializeOnLoadMethod] static void OnRuntimeMethodLoad() { Debug.Log("After Scene is loaded and game is running"); } 

Documentation: https://docs.unity3d.com/ScriptReference/RuntimeInitializeOnLoadMethodAttribute.html

//try this it work in my case public static bool isFirstLoad; void Awake() { //your work that run only once even restart this scene mainPanel.SetActive(!isFirstLoad); if(!isFirstLoad) { isFirstLoad=true; } if (Instance == null) { Instance = this; DontDestroyOnLoad(this.gameObject); } }