Except - 2

public void Linq53()
{
    List products = GetProductList();
    List customers = GetCustomerList();
  
    var productFirstChars =
        from p in products
        select p.ProductName[0];
    var customerFirstChars =
        from c in customers
        select c.CompanyName[0];
  
    var productOnlyFirstChars = productFirstChars.Except(customerFirstChars);
  
    Console.WriteLine("First letters from Product names, but not from Customer names:");
    foreach (var ch in productOnlyFirstChars)
    {
        Console.WriteLine(ch);
    }
}

public void Linq53()
{
    List products = GetProductList();
    List customers = GetCustomerList();
 
    var productFirstChars = products.Select(prod => prod.ProductName[0]);
    var customerFirstChars = customers.Select(cust => cust.CompanyName[0]);
 
    var productOnlyFirstChars = productFirstChars.Except(customerFirstChars);
 
    Console.WriteLine("First letters from Product names, but not from Customer names:");
    foreach (var ch in productOnlyFirstChars)
    {
        Console.WriteLine(ch);
    }
}