UnityEditor.EditorExtensionMethods.GetArrayOrListElementType C# (CSharp) Method

        internal static Type GetArrayOrListElementType(Type listType)
        {
            if (listType.IsArray)
            {
                return listType.GetElementType();
            }
            if (listType.IsGenericType && (listType.GetGenericTypeDefinition() == typeof(List<>)))
            {
                return listType.GetGenericArguments()[0];
            }
            return null;
        }