String Split Remove SOME Empty Entries

[G_Hosa_Phat]

I'm trying to create an extension method for wrapping text to a specific number of characters for display in a console application. For the most part, it works very well, but I've run into a slight issue with how it handles a string that contains line breaks (Environment.NewLine, vbCr, vbLf, vbCrLf). Here's the method I'm currently working with:

<Extension()>
    Public Function Wrap(ByVal Text As String, ByVal Width As Integer, Optional ByVal FullWidthLine As Boolean = False) As String
        Dim InputLines As List(Of String) = Text.Split(New Char() {vbCr, vbLf, vbCrLf, Environment.NewLine}, StringSplitOptions.RemoveEmptyEntries).ToList
        Dim OutputLines As New List(Of String)
 
        For Each Line As String In InputLines
            Dim Words As List(Of String) = Line.Split(CChar(" ")).ToList()
 
            If Line.Length < Width OrElse Words.Count = 1 Then
                If FullWidthLine Then
                    OutputLines.Add(Line.PadRight(Width, " "c))
                Else
                    OutputLines.Add(Line)
                End If
            Else
                Dim CurrentLine As String = Words(0)
 
                For I As Integer = 1 To Words.Count - 1
                    If (CurrentLine & " " & Words(I)).Length > Width Then
                        If FullWidthLine Then
                            OutputLines.Add(CurrentLine.PadRight(Width, " "c))
                        Else
                            OutputLines.Add(CurrentLine)
                        End If
 
                        CurrentLine = Words(I)
 
                        If I = Words.Count - 1 Then
                            If FullWidthLine Then
                                OutputLines.Add(CurrentLine.PadRight(Width, " "c))
                            Else
                                OutputLines.Add(CurrentLine)
                            End If
                        End If
                    Else
                        If I = Words.Count - 1 Then
                            If FullWidthLine Then
                                OutputLines.Add((CurrentLine & " " & Words(I)).PadRight(Width, " "c))
                            Else
                                OutputLines.Add(CurrentLine & " " & Words(I))
                            End If
                        End If
 
                        CurrentLine &= " " & Words(I)
                    End If
                Next I
            End If
        Next
 
        Return String.Join(Environment.NewLine, OutputLines.ToArray())
    End Function

For a string like $"Invalid selection. Option {UserInput} is not available." & vbCrLf & "Please enter the number of the desired menu item from the list below." This works exactly as expected. The output is "wrapped" to two lines and displayed pretty much exactly as it was entered:

Invalid selection. Option 9 is not available.
Please enter the number of the desired menu item from the list below.

However, if I want to add an additional line of space between the two lines like this: $"Invalid selection. Option {UserInput} is not available." & vbCrLf & vbCrLf & "Please enter the number of the desired menu item from the list below." the StringSplitOptions.RemoveEmptyEntries wipes out my "extra" line and I end up with exactly the same thing as before:

Invalid selection. Option 9 is not available.
Please enter the number of the desired menu item from the list below.

Now, this is to be expected because the extra line break is "technically" an empty entry. But, in this case, I actually want that extra bit of space between the two lines.

Invalid selection. Option 9 is not available.

Please enter the number of the desired menu item from the list below.

If I remove the StringSplitOptions.RemoveEmptyEntries parameter from my Split method call (or change it to StringSplitOptions.None), then I end up with additional empty lines in my OutputLines List(Of String) object that "don't belong" there.

So, now I'm just trying to figure out how to build my List(Of String) object, split on any of the new line character(s), preserving blank lines, but not "creating" empty entries.

In my testing, I've tried to do this:

Dim NewLines As Char() = {vbCrLf, vbCr, vbLf, Environment.NewLine}
        Dim TestLines As New List(Of String)
        Dim LastIndex As Integer = 0
        Dim NextIndex As Integer = Text.IndexOfAny(NewLines, LastIndex)
 
        Do While NextIndex > 0
            TestLines.Add(Text.Substring(LastIndex, NextIndex))
            LastIndex = NextIndex + 1
            NextIndex = Text.IndexOfAny(NewLines, LastIndex)
        Loop

But, that ends up creating "duplicate" lines in my list because it's hitting each of the individual new line characters - vbCr (Chr(13)) and vbLf (Chr(10)) - and creating a new line for that. I tried just using Environment.NewLine or vbCrLf, but those don't seem to catch things correctly either and I end up with just two lines - everything up to the first line break, then one for everything after the new line characters at the beginning. It's still not what I'm after and I'm just not sure how to get there. Any assistance would be greatly appreciated.

[techgnome]

So, if I'm reading right... sometimes you want to remove the empty lines ... other times not ... Would an optional flag PreserveEmpty work? Default to false. False would include the RemoveemptyEntries, while True wouldn't.

-tg

[G_Hosa_Phat]

Sorta, but sorta not. Let me see if I can explain it a bit better:

Here's the string I'm testing with:

$"Invalid selection. Option {UserInput} is not available." & vbCrLf & vbCrLf & "Please enter the number of the desired menu item from the list below."

Using the String.Split() method with the StringSplitOptions.None option, I get the following five entries added to my list:

[0] "Invalid selection. Option 9 is not available."
[1] ""
[2] ""
[3] ""
[4] "Please enter the number of the desired menu item from the list below."

With the StringSplitOptions.RemoveEmptyEntries option, I get just two entries added to the list:

[0] "Invalid selection. Option 9 is not available."
[1] "Please enter the number of the desired menu item from the list below."

What I WANT is three entries in the list like this:

[0] "Invalid selection. Option 9 is not available."
[1] ""
[2] "Please enter the number of the desired menu item from the list below."

Does that help clarify what I'm trying to accomplish?

ADDITIONAL TESTING:
I almost thought I had the solution by using Regex.Split() instead of String.Split():

Dim InputLines As List(Of String) = System.Text.RegularExpressions.Regex.Split(Text, vbCrLf).ToList

This worked great for my original testing string above, but it "failed" when I changed the vbCrLf characters to just vbLf. Because I don't want it to break apart the vbCrLf into two separate new line characters but I still want it to split on any individual new line characters, I guess I need to find a way to "normalize" the line breaks so the Split() method (whichever one works best in this case) can pick them up properly. Unless there's a way to "prioritize" the separators in a split operation so it looks for the vbCrLf before trying to find either the vbLf or vbCr.

Of course, now that I'm thinking of it, I suppose I could do it in two passes: the first pass splits on the vbCrLf, then it goes through each of those lines and splits them on either the vbCr or vbLf...

[techgnome]

How often will you have a CR or LF that's not a CRLF?

-tg

[G_Hosa_Phat]

If I'm writing the code, virtually never. But, I'm trying to build this as an extension in a library that might be used by someone else or might be taking input from a source (like a file or something) where I can't necessarily control what line break characters are coming in.

But... I think I've found a solution. It's a little "wonky", but it seems to work for the situation. I'm "normalizing" the input text by converting all new line characters to vbLf:

Dim NormalizedText As String = Text.Replace(vbCrLf, vbLf).Replace(vbCr, vbLf)

This way, I don't have to worry about it breaking up a vbCrLf and creating "extra" entries. Once the text is "normalized", I then use the Regex.Split() method from above to split it on the vbLf character only, and voilà, I have three entries in my list!

Dim InputLines As List(Of String) = System.Text.RegularExpressions.Regex.Split(NormalizedText, vbLf).ToList

Even if I change the testing string to use a combination of vbCrLf, vbLf, or vbCr, it seems to finally be doing what I was trying to achieve!

So, here's what I've come up with:

<Extension()>
Public Function Wrap(ByVal Text As String, ByVal Width As Integer, Optional ByVal FullWidthLine As Boolean = False) As String
    Dim NormalizedText As String = Text.Replace(vbCrLf, vbLf).Replace(vbCr, vbLf)
    Dim InputLines As List(Of String) = System.Text.RegularExpressions.Regex.Split(NormalizedText, vbLf).ToList
    Dim OutputLines As New List(Of String)
 
    For Each Line As String In InputLines
        Dim Words As List(Of String) = Line.Split(CChar(" ")).ToList()
 
        If Line.Length < Width OrElse Words.Count = 1 Then
            If FullWidthLine Then
                OutputLines.Add(Line.PadRight(Width, " "c))
            Else
                OutputLines.Add(Line)
            End If
        Else
            Dim CurrentLine As String = Words(0)
 
            For I As Integer = 1 To Words.Count - 1
                If (CurrentLine & " " & Words(I)).Length > Width Then
                    If FullWidthLine Then
                        OutputLines.Add(CurrentLine.PadRight(Width, " "c))
                    Else
                        OutputLines.Add(CurrentLine)
                    End If
 
                    CurrentLine = Words(I)
 
                    If I = Words.Count - 1 Then
                        If FullWidthLine Then
                            OutputLines.Add(CurrentLine.PadRight(Width, " "c))
                        Else
                            OutputLines.Add(CurrentLine)
                        End If
                    End If
                Else
                    If I = Words.Count - 1 Then
                        If FullWidthLine Then
                            OutputLines.Add((CurrentLine & " " & Words(I)).PadRight(Width, " "c))
                        Else
                            OutputLines.Add(CurrentLine & " " & Words(I))
                        End If
                    End If
 
                    CurrentLine &= " " & Words(I)
                End If
            Next I
        End If
    Next
 
    Return String.Join(Environment.NewLine, OutputLines.ToArray())
End Function

I suppose I just needed to talk it out a bit.