Question

I am trying to group by my table with multiple columns and checking if the grouping count is equal to 2. I have the query working for this part

var query = from product in Products
            group by new { product.Product, product.Location, product.Customer } into grp
            where grp.Count() != 2

The Product has an another property Category, which could only have two values “High” & “Low”.
How can I change this query to handle the check for Category in addition to the grouping count.

Product    Location   Customer    Category
  A           X         C1          High
  A           X         C1          Low
  A           Y         C1          High
  A           Y         C1          Low
  A           Y         C1          Low
  B           X         C1          High
  B           X         C1          Medium

In the example above, except for Product A at Location X and Customer C1, all other records are invalid. The Location Y has two Lows and Product B has a category Medium which is not part of the list: High & Low.

Answer 1

If you want to include only specific categories, use a where .. expression:

var query = from product in Products
            where product.Category == "Low" || product.Category == "High"
            group ...