Extension method not visible in Inspector

I’ve created an extension method for CanvasGroup that can be called from code and works fine, but doesn’t show up when trying to assign it to a button’s OnClick() event. It’s not visible in the list of functions in the inspector. Am I missing a tag like [SerializeField] or something above the method or class containing the extension? Thanks.

public static class CanvasGroupFadeExt
{
    public static void Fade(this CanvasGroup obj, float speed)
    {
        UIFunction.Fade(obj, speed, true);
    }
}

Extension methods are static methods which does not belong to the type. Yes, you can call GetComponent<CanvasGroup>().Fade( value ), but behind the scene, it’s the static method which is called.

When listing the methods in the inspector, Unity retrieves only the methods which:

- are not static

- declared public

- have a return type of void

- takes one or one parameter (parameter must be of type float, int, string, bool, UnityEngine.Object)