String concatenation using LINQ to create a CSV/PSV string

public static string Join<T>(this IList<T> list, string joinString)
    {
        StringBuilder result = new StringBuilder();

        int listCount = list.Count;
        int listCountMinusOne = listCount - 1;

        if (list != null && listCount > 0)
        {
            if (listCount > 1)
            {
                for (var i = 0; i < listCount; i++)
                {
                    if (i != listCountMinusOne)
                    {
                        result.Append(list[i]);
                        result.Append(joinString);
                    }
                    else
                        result.Append(list[i]);
                }
            }
            else
                result.Append(list[0]);
        }

        return result.ToString();
    }