如何在LINQ选择中访问循环索引？

Question

这段代码:

var customers = from cust in Customers
    group cust by new {cust.Country} into grouping
    select new
    {
        Country = grouping.Key.Country,
        Customers = grouping
    };

customers.ToList().ForEach(g => 
    Console.WriteLine("{0} has {1} customers: {2}", 
        g.Country, 
        g.Customers.Count(), 
        String.Join(", ",g.Customers.Select(x => "#. " + x.CompanyName).ToArray())
    ));

customers.Dump();

产生这些结果:

Argentina has 3 customers: #. Cactus Comidas para llevar, #. Océano Atlántico Ltda., #. Rancho grande
Austria has 2 customers: #. Ernst Handel, #. Piccolo und mehr
Belgium has 2 customers: #. Maison Dewey, #. Suprêmes délices
Brazil has 9 customers: #. Comércio Mineiro, #. Familia Arquibaldo, #. Gourmet Lanchonetes, #. Hanari Carnes, #. Que Delícia, #. Queen Cozinha, #. Ricardo Adocicados, #. Tradição Hipermercados, #. Wellington Importadora
Canada has 3 customers: #. Bottom-Dollar Markets, #. Laughing Bacchus Wine Cellars, #. Mère Paillarde
Denmark has 2 customers: #. Simons bistro, #. Vaffeljernet
...

如何用索引/计数替换"#",以便得到如下结果:

Argentina has 3 customers: 1. Cactus Comidas para llevar, 2. Océano Atlántico Ltda., 3. Rancho grande
...

Answer 1

customers.ToList().ForEach(g => Console.WriteLine("{0} has {1} customers: {2}",
    g.Country, 
    g.Customers.Count(), 
    string.Join(", ",
        g.Customers.Select((x, i) => i + ". " + x.CompanyName).ToArray())));