A simple extension method for Unity C# this gets or adds a given Component. (SphereCollider coll = gameObject.GetOrAddComponent<SphereCollider>();)

GetOrAddComponent.cs

public static class Extensions
{
    public static T GetOrAddComponent<T>(this GameObject gameObject) where T : Component
    {
        if(gameObject.TryGetComponent<T>(out T t))
        {
            return t;
        }
        else
        {
            return gameObject.AddComponent<T>();
        }
    }
}

A simple extension method that saved me countless lines of redundant code