string Join(this IEnumerable sequence, string seperator);

which means you can write;

string delimitedids = ids.Select(x => x.ToString()).Join(“, “);

Here’s the implementation using a stringbuilder;

public static string Join(this IEnumerable strings, string seperator)
{
IEnumerator en = strings.GetEnumerator();
StringBuilder sb = new StringBuilder();
if (en.MoveNext())
{
// we have at least one item.
sb.Append(en.Current);
}
while (en.MoveNext())
{
// second and subsequent get delimiter
sb.Append(seperator).Append(en.Current);
}
return sb.ToString();
}

I tend to use this all the time when putting together code that generates descriptions; debug messages, ToStrings, that kind of thing.