Extension methods that converts a sequence (IEnumerable<>) of objects to a delimited string. Includes a generic method.

ToDelimitedStringExtensions.cs

public static class ExtensionMethods 
{
    /// <summary>
    /// Converts an <see cref="IEnumerable{T}"/> of <see cref="string"/>s to a flat string, delimited by a delimiter string.
    /// </summary>
    /// <param name="stringEnumerable"></param>
    /// <param name="delimiter">Defaults to comma with a space (, )</param>
    /// <param name="openEncloseString">Enclose each string in the IEnumerable inside two other strings. e.g. an apostrophe will produce: ('a', 'b', 'c')</param>
    /// <param name="closeEncloseString"></param>
    /// <returns></returns>
    public static string ToDelimitedString(this IEnumerable<string> stringEnumerable, string delimiter = ", ", string openEncloseString = "", string closeEncloseString = "")
    {
        var result = "";
        var enumerable = stringEnumerable as string[] ?? stringEnumerable.ToArray();
        var lastIndex = enumerable.Length - 1;
        for (var i = 0; i < enumerable.Length; i++)
        {
            var individualString = enumerable.ElementAt(i);
            // enclose each string if need be
            if (!string.IsNullOrWhiteSpace(openEncloseString)) individualString = $"{openEncloseString}{individualString}{closeEncloseString}";
            // dont add the delimiter to the very last one
            if (i != lastIndex)
                result = result + $"{individualString}{delimiter}";
            else
                result = result + individualString;
        }
        return result;
    }

    /// <summary>
    /// Generic wrapper method for <see cref="ToDelimitedString"/>. Invokes the <see cref="object.ToString"/> method on each element in the sequence.
    /// </summary>
    /// <typeparam name="TType"></typeparam>
    /// <param name="theEnumerableOfThings"></param>
    /// <param name="delimiter"></param>
    /// <param name="openEncloseString"></param>
    /// <param name="closeEncloseString"></param>
    /// <returns></returns>
    public static string ToDelimitedString<TType>(this IEnumerable<TType> theEnumerableOfThings, string delimiter = ", ", string openEncloseString = "",
        string closeEncloseString = "")
    {
        var castedEnumerable = theEnumerableOfThings.Select(thing => thing.ToString());

        return castedEnumerable.ToDelimitedString(delimiter, openEncloseString, closeEncloseString);
    }
}