Convert text ranges to int array and back

RangesToArray

public static int[] ToIntArray(this string text)
        {
            if (string.IsNullOrWhiteSpace(text))
            {
                return new int[]
                {
                };
            }
            List<int> result = new List<int>();
            string[] ranges = text.Split(',');
            foreach (string range in ranges)
            {
                string[] pair = range.Split('-');
                if (pair.Length == 1)
                {
                    result.Add(int.Parse(pair[0]));
                }
                if (pair.Length == 2)
                {
                    int min = int.Parse(pair[0]);
                    int max = int.Parse(pair[1]);
                    result.AddRange(Enumerable.Range(min, max - min + 1));
                }
            }
            return result.ToArray();
        }

        public static string ToRanges(this int[] array)
        {
            if (array == null || array.Length == 0)
            {
                return string.Empty;
            }

            StringBuilder sb = new StringBuilder();
            Array.Sort(array);

            int predItem = int.MinValue;
            int seqLength = 0;
            int nextInt = int.MinValue;
            for (int index = 0; index < array.Length; index++)
            {
                if (nextInt != array[index])
                {
                    if (sb.Length == 0)
                    {
                        sb.Append(array[index]);
                    }
                    else if (seqLength == 0)
                    {
                        sb.AppendFormat(",{0}", array[index]);
                    }
                    else
                    {
                        sb.AppendFormat("-{0},{1}", predItem, array[index]);
                    }
                    seqLength = 0;
                }
                else
                {
                    seqLength++; // sequence of items which goes 1 by 1

                    if (index == array.Length - 1)
                    {
                        sb.AppendFormat("-{0}", array[index]);
                    }
                }
                predItem = array[index];
                nextInt = array[index] + 1;
            }
            return sb.ToString();
        }
/// tests xUnit        
[Theory]
        [InlineData("1,2,3-5,7,9-14", new[]{1, 2, 3, 4, 5, 7, 9, 10, 11, 12, 13, 14})]
        [InlineData("1", new[]{1})]
        [InlineData("1,2", new[]{1,2})]
        [InlineData("1-5", new[]{1, 2, 3, 4, 5})]
        [InlineData("1,3,5,7", new[]{1, 3, 5, 7})]
        [InlineData("1,5-7,9", new[]{1, 5, 6, 7, 9})]
        public void ToIntArray_should_convert_rages_to_intArray(string ranges, int[] expected)
        {
            int[] actual = ranges.ToIntArray();

            Assert.True(expected.SequenceEqual(actual));
        }

        [Theory]
        [InlineData(new[]{1, 2, 3, 4, 5, 7, 9, 10, 11, 12, 13, 14}, "1-5,7,9-14")]
        [InlineData(new[]{1}, "1")]
        [InlineData(new[]{1, 2}, "1-2")]
        [InlineData(new[]{1, 3, 5, 7, 9}, "1,3,5,7,9")]
        [InlineData(new[]{1, 5, 6, 7, 9}, "1,5-7,9")]
        public void ToRanges_should_convert_intArray_to_ranges(int[] array, string expected)
        {
            string actual = array.ToRanges();

            Assert.Equal(expected, actual);
        }