List<long> to comma delimited string in C#

This often comes up. I h开发者_C百科ave a List and I want to go to a comma delimited string of all the elements in the list that I can use in SQL.

What is the most elegant way to do this in C#? Iterating over all of them is fine, except either the first or last element has to be special-cased since I don't want leading or trailing commas.

Got a good one-liner?

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string.Join is your friend...

var list = new List<long> {1, 2, 3, 4};
var commaSeparated = string.Join(",", list);

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List<long> items = // init here
string result = string.Join(", ", items.Select(i => i.ToString()).ToArray());

Not sure if it's the most elegant way, but it is a 1 liner!

Now there is also a string.Join that accepts an IEnumerable<T>, so it gets even shorter:

string result = string.Join(", ", items);

Thanks to type inference, you don't need to specified Join<long>

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string.Join(",", Array.ConvertAll(list.ToArray(), item => item.ToString()));

(written directly into the post, so I may have got a couple of the parameters wrong, but you get the idea)

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If you were to do it manually you shouldn't have special cases for both first and last value, instead you could just do this:

List<long> junk = // have some values here;
string separator = string.Empty;
string list = string.Empty;

foreach(long john in junk)
{
    list += separator + john.ToString();
    separator = ", ";
}

Not saying you should do this, regard this just as a comment.

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// Content IDs
List<long> cIds = new List<long>();
cIds.Add(1);
cIds.Add(2);
cIds.Add(1);
cIds.Add(3);
cIds.Add(3);
string ids = string.Join(",", cIds.Distinct().Select(x => x.ToString()).ToArray());
// The example return the following output:
// ids = "1,2,3"

returns a list of unique items comma delimited.

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    public static string CommaSeparate(this IEnumerable<string> values)
    {
        if (values.Count() == 0) return "[none]";
        return string.Join(", ", values.ToArray());
    }

This is an extension method that I use to do this in my applications. It's based on IEnumerable but should be similar for List.

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I believe String.Join does that.

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List<long> list =new List<long>(){1,2,3,4,5,6,7};

StringBuilder str =new StringBuilder();    

foreach(var i in list)
{
str.Append(i).Append(',');
}

This will Append the long values in (stringBuilder) str as

Ans: str = 1,2,3,4,5,6,7