Table 'Worktable'. Scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table '#source'. Scan count 1, logical reads 77, physical reads 0, read-ahead reads 0, lob logical reads 3803, lob physical reads 0, lob read-ahead reads 2381.

SQL Server Execution Times:
   CPU time = 1422 ms,  elapsed time = 1940 ms.

public partial class UserDefinedFunctions
{
    [Microsoft.SqlServer.Server.SqlFunction(
        FillRowMethodName = "FillRow",
        DataAccess = DataAccessKind.None,
        SystemDataAccess = SystemDataAccessKind.None,
        Name = "tfn_Split",
        TableDefinition = "row_id int, result nvarchar(max)")]
    public static IEnumerable tfn_Split
        (
        [SqlFacet(IsNullable = false, MaxSize = -1, IsFixedLength = false)]
        SqlString StringToSplit,
        [SqlFacet(IsNullable = false, MaxSize = 4000, IsFixedLength = false)]
        SqlString Delimiter
        )
    {
        string toSplit = StringToSplit.Value;
        string delimeter = Delimiter.Value;

        string[] items = toSplit.Split(new string[] { delimeter }, StringSplitOptions.RemoveEmptyEntries);
        Dictionary (items.Length);
        for (int i = 0; i < items.Length; i++)
        {
            results.Add(i + 1, items[i]);
        }
        return results;
    }

    public static void FillRow(Object obj, out SqlInt32 row_id, out SqlString result)
    {
        KeyValuePair )obj;
        row_id = new SqlInt32(kvp.Key);
        result = new SqlString(kvp.Value);
    }
};

SELECT	S.row_id, TVF.row_id, TVF.result
FROM	#source AS S
CROSS
APPLY	dbo.tfn_Split(S.definition, CHAR(13) + CHAR(10)) AS TVF
ORDER	BY
		S.row_id, TVF.row_id;

DELETE FROM @result  -- Clean up

-- //////////////////////////////////////////////////////////
-- -> Clr xml solution
PRINT 'Start clr xml solution'
SELECT @now = GETDATE()

-- Split text into lines
INSERT INTO @result 
   SELECT l.line
   FROM @source s
      CROSS APPLY (SELECT
                      ISNULL(T.C.value('(./text())[1]', 'nvarchar(1000)'), '') line
                   FROM (SELECT dbo.ufn_clr_SplitLines(s.definition) col1) x
                      CROSS APPLY x.col1.nodes('/Root/Item') T(C)
                  ) l

-- Results
SELECT @duration = DATEDIFF(MILLISECOND, @now, GETDATE())
SELECT @count = COUNT(*) FROM @result
PRINT 'Milliseconds: ' + CONVERT(VARCHAR(10), @duration) + ' | Lines: ' + CONVERT(VARCHAR(10), @count)
-- <- Clr xml solution
-- //////////////////////////////////////////////////////////