Implement “not in” (aka “not exists”) logic in LINQ

Question

Setup

1. I have two List\'s.
2. The data is un-normalized and from different sources which explains the convolution in the desired logic

Answer 1

SQL to LINQ ( Case 7 - Filter data by using IN and NOT IN clause)

Note: IN and NOT IN use the same function in the LINQ query, but it just use a ! (not) symbol for it. Here is the graphical representation:

You use, where .Contains( )

var myProducts = from p in db.Products
                 where productList.Contains(p.ProductID)
                 select p;

Or you can have a list predefined as such:

var ids = {1, 2, 3};

var query = from item in context.items
            where ids.Contains( item.id )
            select item;

For the 'NOT' case, just add the '!' operator before the 'Contains' statement.