Putting a Separator Between Your Elements

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Often when I’m programming, I’ll need to list a bunch of stuff and put commas between them. Like this:

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1,2,3,4,5

Usually, this is what I, and most of my colleagues do:

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        List<int> nums = new List<int>();
        for (int i = 0; i < 5; i++)
        {
            nums.Add(i);
        }

        string msg = "";
        bool first = true;
        foreach (int num in nums)
        {
            if (first)
            {
                first = false;
            }
            else
            {
                msg += ",";
            }
            msg += num.ToString();
        }

After reading Eric Lippert’s little article about the horrid-seeming problem of commas and lists, I noticed him mentioning the method

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String.Join

Needless to say, I went and tried it, and found that I could do the equivalent of the above, like this:

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        List<int> nums = new List<int>();
        for (int i = 0; i < 5; i++)
        {
            nums.Add(i);
        }

        string msg = string.Join(",", nums.Select(x => x.ToString()).ToArray());
        Console.WriteLine(msg);

Its kinda amazing how after coding in C# for a good year now that I haven’t noticed the existence of such a method.

Okay, the lambda expression seems a bit messy with all the parens and all, but you get the idea. Still, its a lot better than writing a loop and having the evil “first” variable which kinda clutters the whole thing. Does anyone know an even better way of doing this?

Update: and for my answer to Eric’s next post:

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string msg = "{";
IEnumerable<string> s = something;

string[] arr = s.ToArray();

if (arr.Length > 1)
{
    string[] ar2 = {
               string.Join(", ", arr, 0, arr.Length - 1 ),
                arr[arr.Length - 1]
           };

    msg += string.Join(" and ", ar2);
}
else if (arr.Length == 1) msg += arr[0];

msg += "}";

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