How to convert IEnumerable<string> to one comma separated string?

using System;
using System.Collections.Generic;
using System.Linq;

class C
{
    public static void Main()
    {
        var a = new []{
            "First", "Second", "Third"
        };

        System.Console.Write(string.Join(",", a));

    }
}

string output = String.Join(",", yourEnumerable);

String.Join Method (String, IEnumerable

Concatenates the members of a constructed IEnumerable collection of type String, using the specified separator between each member.

collection.Aggregate("", (str, obj) => str + obj.ToString() + ",");