Join a string using delimiters

Question

What is the best way to join a list of strings into a combined delimited string. I\'m mainly concerned about when to stop adding the delimiter. I\'ll use C# for my example

Answer 1

It's impossible to give a truly language-agnostic answer here as different languages and platforms handle strings differently, and provide different levels of built-in support for joining lists of strings. You could take pretty much identical code in two different languages, and it would be great in one and awful in another.

In C#, you could use:

StringBuilder builder = new StringBuilder();
string delimiter = "";
foreach (string item in list)
{
    builder.Append(delimiter);
    builder.Append(item);
    delimiter = ",";       
}
return builder.ToString();

This will prepend a comma on all but the first item. Similar code would be good in Java too.

EDIT: Here's an alternative, a bit like Ian's later answer but working on a general IEnumerable.

// Change to IEnumerator for the non-generic IEnumerable
using (IEnumerator iterator = list.GetEnumerator())
{
    if (!iterator.MoveNext())
    {
        return "";
    }
    StringBuilder builder = new StringBuilder(iterator.Current);
    while (iterator.MoveNext())
    {
        builder.Append(delimiter);
        builder.Append(iterator.Current);
    }
    return builder.ToString();
}

EDIT nearly 5 years after the original answer...

In .NET 4, string.Join was overloaded pretty significantly. There's an overload taking IEnumerable which automatically calls ToString, and there's an overload for IEnumerable. So you don't need the code above any more... for .NET, anyway.