Any - Grouped

Query

public void Linq69()
{
    List products = GetProductList();
    var productGroups =
        from p in products
        group p by p.Category into g
        where g.Any(p => p.UnitsInStock == 0)
        select new { Category = g.Key, Products = g };
 
    ObjectDumper.Write(productGroups, 1); 
}

Lambda Expression

public void Linq69()
{
    List products = GetProductList();
 
    var productGroups =
        products.GroupBy(prod => prod.Category)
        .Where(prodGroup => prodGroup.Any(p => p.UnitsInStock == 0))
        .Select(prodGroup => new {
            Category = prodGroup.Key,
            Products = prodGroup});
 
    ObjectDumper.Write(productGroups, 1);
}

Output

Category=Condiments Products=...
Products: ProductID=3 ProductName=Aniseed Syrup Category=Condiments UnitPrice=10.0000 UnitsInStock=13
Products: ProductID=4 ProductName=Chef Anton's Cajun Seasoning Category=Condiments UnitPrice=22.0000 UnitsInStock=53
Products: ProductID=5 ProductName=Chef Anton's Gumbo Mix Category=Condiments UnitPrice=21.3500 UnitsInStock=0
Products: ProductID=6 ProductName=Grandma's Boysenberry Spread Category=Condiments UnitPrice=25.0000 UnitsInStock=120
Products: ProductID=8 ProductName=Northwoods Cranberry Sauce Category=Condiments UnitPrice=40.0000 UnitsInStock=6
Products: ProductID=15 ProductName=Genen Shouyu Category=Condiments UnitPrice=15.5000 UnitsInStock=39
Products: ProductID=44 ProductName=Gula Malacca Category=Condiments UnitPrice=19.4500 UnitsInStock=27
Products: ProductID=61 ProductName=Sirop d'Ã©rable Category=Condiments UnitPrice=28.5000 UnitsInStock=113
Products: ProductID=63 ProductName=Vegie-spread Category=Condiments UnitPrice=43.9000 UnitsInStock=24
Products: ProductID=65 ProductName=Louisiana Fiery Hot Pepper Sauce Category=Condiments UnitPrice=21.0500 UnitsInStock=76
Products: ProductID=66 ProductName=Louisiana Hot Spiced Okra Category=Condiments UnitPrice=17.0000 UnitsInStock=4
Products: ProductID=77 ProductName=Original Frankfurter grÃ¼ne SoÃŸe Category=Condiments UnitPrice=13.0000 UnitsInStock=32
Category=Meat/Poultry Products=...
Products: ProductID=9 ProductName=Mishi Kobe Niku Category=Meat/Poultry UnitPrice=97.0000 UnitsInStock=29
Products: ProductID=17 ProductName=Alice Mutton Category=Meat/Poultry UnitPrice=39.0000 UnitsInStock=0
Products: ProductID=29 ProductName=ThÃ¼ringer Rostbratwurst Category=Meat/Poultry UnitPrice=123.7900 UnitsInStock=0
Products: ProductID=53 ProductName=Perth Pasties Category=Meat/Poultry UnitPrice=32.8000 UnitsInStock=0
Products: ProductID=54 ProductName=TourtiÃ¨re Category=Meat/Poultry UnitPrice=7.4500 UnitsInStock=21
Products: ProductID=55 ProductName=PÃ¢tÃ© chinois Category=Meat/Poultry UnitPrice=24.0000 UnitsInStock=115
Category=Dairy Products Products=...
Products: ProductID=11 ProductName=Queso Cabrales Category=Dairy Products UnitPrice=21.0000 UnitsInStock=22
Products: ProductID=12 ProductName=Queso Manchego La Pastora Category=Dairy Products UnitPrice=38.0000 UnitsInStock=86
Products: ProductID=31 ProductName=Gorgonzola Telino Category=Dairy Products UnitPrice=12.5000 UnitsInStock=0
Products: ProductID=32 ProductName=Mascarpone Fabioli Category=Dairy Products UnitPrice=32.0000 UnitsInStock=9
Products: ProductID=33 ProductName=Geitost Category=Dairy Products UnitPrice=2.5000 UnitsInStock=112
Products: ProductID=59 ProductName=Raclette Courdavault Category=Dairy Products UnitPrice=55.0000 UnitsInStock=79
Products: ProductID=60 ProductName=Camembert Pierrot Category=Dairy Products UnitPrice=34.0000 UnitsInStock=19
Products: ProductID=69 ProductName=Gudbrandsdalsost Category=Dairy Products UnitPrice=36.0000 UnitsInStock=26
Products: ProductID=71 ProductName=Flotemysost Category=Dairy Products UnitPrice=21.5000 UnitsInStock=26
Products: ProductID=72 ProductName=Mozzarella di Giovanni Category=Dairy Products UnitPrice=34.8000 UnitsInStock=14