>Now that we are clear on what Michel actually wants in the result the shortest solution seems to be:

>string[] delimiters = new string[] { Environment.NewLine };   //may be safer than "\r\n" ?
>string[] lines = TestString.Split(delimiters,StringSplitOptions.None);

>Again I don't know if performance will be an issue but with 100000 lines of about 100 characters each this is still a sub-millisecond operation on my (average) machine. Ran out of ram trying a million lines tho :-{
>Update: Your version using fluent syntax took pretty much the same time:

string[] lines = TestString.Replace("\r",String.Empty).Split("\n".ToCharArray());

Using that approach, it resolves the issue.

        ' Load the string into the string builder
        ' expC1 String
        Public Function LoadString(ByVal tcString As String) As Boolean
            Dim lcDelimiter As String() = New String() {Environment.NewLine}

            ' Make sure to clear the string builder
            oStringBuilder.Length = 0

            oStringBuilder.Append(tcString)

            ' Initialize the array
            oLine = oStringBuilder.ToString.Split(lcDelimiter, StringSplitOptions.None)

            ' Count the number of lines
            nLine = MemLines()

            Return (True)
        End Function

        ' Return the number of lines in a string
        Public Function MemLines() As Integer
            Return oLine.Length
        End Function

        ' Return the specific line in a string
        ' expN1 Line
        Public Function MLine(ByVal tnLine As Integer) As Boolean

            ' Reset the values
            cLine = ""

            ' If the value passed is smaller or eqaul to the number of lines
            If tnLine - 1 <= nLine Then
                cLine = oLine(tnLine - 1)
            End If

            Return True
        End Function

Before, I was using a direct reference to Environment.NewLine.ToCharArray in this line:

            oLine = oStringBuilder.ToString.Split(Environment.NewLine.ToCharArray, StringSplitOptions.None)

Now, I am using the String() approach. So, maybe this is why it didn't work before.

Thanks