Join collection of objects into comma-separated string

I found string.Join and lambda Select<Func<>> helps to write minimum code.

List<string> fruits = new List<string>();
fruits.Add("Mango");
fruits.Add("Banana");
fruits.Add("Papaya");

string commaSepFruits = string.Join(",", fruits.Select(f => "'" + f + "'"));
Console.WriteLine(commaSepFruits);

List<int> ids = new List<int>();
ids.Add(1001);
ids.Add(1002);
ids.Add(1003);

string commaSepIds = string.Join(",", ids);
Console.WriteLine(commaSepIds);

List<Customer> customers = new List<Customer>();
customers.Add(new Customer { Id = 10001, Name = "John" });
customers.Add(new Customer { Id = 10002, Name = "Robert" });
customers.Add(new Customer { Id = 10002, Name = "Ryan" });

string commaSepCustIds = string.Join(", ", customers.Select(cust => cust.Id));
string commaSepCustNames = string.Join(", ", customers.Select(cust => "'" + cust.Name + "'"));

Console.WriteLine(commaSepCustIds);
Console.WriteLine(commaSepCustNames);

Console.ReadLine();

string.Join(", ", Array.ConvertAll(somelist.ToArray(), i => i.ToString()))

static string ToCsv<T>(IEnumerable<T> things, Func<T, string> toStringMethod)
{
    StringBuilder sb = new StringBuilder();

    foreach (T thing in things)
        sb.Append(toStringMethod(thing)).Append(',');

    return sb.ToString(0, sb.Length - 1); //remove trailing ,
}

Use like this:

DataTable dt = ...; //datatable with some data
Console.WriteLine(ToCsv(dt.Rows, row => row["ColName"]));

or:

List<Customer> customers = ...; //assume Customer has a Name property
Console.WriteLine(ToCsv(customers, c => c.Name));

I don't have a compiler to hand but in theory it should work. And as everyone knows, in theory, practice and theory are the same. In practice, they're not.