I want to update product price list item using plugin code

I have added product Price list item in product entity successfully using early bound class library.

I want to update product price list item specific field like amount and unit using plugin code. I am using early bound class library. There are two way which I have used to update product price list item but did not work.

1. First way

   1. I have used linq query to get product.

   2. I want to get list of this product price list item. I have checked all property of product. I did not found any list that have price list item.

2. Seconday way

    1. I have used linq query to get Price list of CRM.

    2. I want to get product which already in this price list but did not found.

Please let us know if you have any solution for that.