ADO.NET :: Using Categories To Get Products?

I am having problems in getting product data when using different levels of categories. My knowledge of SQL is also very limited.

Here is what i have so far

TABLES
Categories
CategoryID (PK) int
CategoryName nvchar(max) allow null
ParentID int allow null
Data for this table
1,Soaps,null
2,Original Range,1
3,Premium Range,1
4,Speciality Range,1
5,Seasonal Collection,4
6,Selection,4
Products
ProductID (PK) int
ProductName nvarchar(max)
ProductDescription nvarchar(max) allow null
ProductPrice money
CategoryID int

Data for this table

1,Prod1,some text,0.25,6
2,Prod2,some text,0.25,6

I have some linq to sql in the page load event that populates a list view,

[Code]....

Now when the category passed in from the query string is 6 then the products with a category of are shown correctly but category 6 is a child category of 4 and 4 is a child of 1 so when i pass in 4 as the category i should still be retrieving the data for products 1 and 2.