title: C# filter list, All or with given value
body: <p>In my list, each list item consist of 2 properties
  ProductCategory
  ProductId</p>
  <p>In my items there is not 0 valued neither ProductId nor ProductCategory</p>
  <p>If client sends me as
  ProductId = 0
  Product Category = 0</p>
  <p>So must return all items in the list</p>
  <p>If client sends me as
  ProductId = 2
  ProductCategory = 0
  I must return
  Only 2 id product in all of the ProductCategory</p>
  <p>Or</p>
  <pre><code>ProductId=0
  ProductCategory=2
  I must return all of the products in 2 id ProductCategory..
  </code></pre>
  <p>Or
  ProductId=3
  ProductCategory=2</p>
  <pre><code> Return productId = 2 in product category 2
  </code></pre>
  <p>How can implement this code without using if else blocks? I have achieved this with 4 if/else blocks but I want to learn is there any better way</p>