VB.NET remove extra blank lines from file

[terryb]

Hello,

I have a file with multiple blank lines in it and I am trying to remove all extra blank lines. Single blank lines need to be preserved but anything more than one needs to be removed so the resulting output is just one blank line between output.

example in:
1

2


3



4

example out:
1

2

3

4


The code I have removes all blank lines.
1
2
3
4

<code>

Imports System
Imports System.IO
Imports System.Collections
Imports System.Text
Imports Microsoft.VisualBasic

Module Module1
Sub Main()

' Create an empty string array to return to caller.
Dim lines() As String = {}

' Check to see if the file exists.
If IO.File.Exists("C:\test.txt") Then

' Open a stream reader to get the text from the file.
Dim sr As New IO.StreamReader("C:\test.txt")

' Read all the file text.
Dim fileText As String = sr.ReadToEnd()

' Split the text into a string array delimited by Carriage Return/Line Feed.
lines = fileText.Split(vbCrLf)

' Close the stream reader
sr.Close()

' Return
Dim sw As New System.IO.Filestream("C:\test1.txt", IO.FileMode.Create)
Dim w as New System.IO.Streamwriter(sw)
Dim i as integer

for i=0 to Ubound(lines)
if lines(i).length > 1 then
w.Write(lines(i))
w.Flush()
end if
next
sw.Close()
End If

End Sub
End Module


</code>

this following vbscript works - but I need it in .NET

Const ForReading = 1
Const ForWriting = 2

Set objFSO = CreateObject("Scripting.FileSystemObject")
Set objFile = objFSO.OpenTextFile("C:\test.txt", ForReading)

strContents = objFile.ReadAll()
objFile.Close

strNewText = vbCrLf & vbCrLf
strOldText = vbCrLf & vbCrLf & vbCrLf
strOldText1 = vbCrLf & vbCrLf & vbCrLf & vbCrLf
strOldText2 = vbCrLf & vbCrLf & vbCrLf & vbCrLf & vbCrLf
strOldText3 = vbCrLf & vbCrLf & vbCrLf & vbCrLf & vbCrLf & vbCrLf

strContents1 = Replace(strContents, strOldText3, strNewText)
strContents2 = Replace(strContents1, strOldText2, strNewText)
strContents3 = Replace(strContents2, strOldText1, strNewText)
strContents = Replace(strContents3, strOldText, strNewText)

Set objFile = objFSO.OpenTextFile("C:\test1.txt", ForWriting)
objFile.Write strContents
objFile.Close


Thanks for any help.

Terry B

[Phil Weber]

' Create an empty string array to return to caller.
Dim lines() As String = {}

' Check to see if the file exists.
Dim FileName As String = "c:\test.txt"
If File.Exists(FileName) Then
    ' Open a stream reader to get the text from the file.
    Dim sr As New StreamReader(FileName)
    ' Read all the file text.
    Dim fileText As String = sr.ReadToEnd()
    ' Close the stream reader
    sr.Close()

    ' Split the text into a string array delimited by Carriage Return/Line Feed.
    lines = Split(fileText, vbCrLf)

    ' Return
    Dim fs As New FileStream("c:\test1.txt", FileMode.Create)
    Dim sw As New StreamWriter(fs)

    Dim foundBlank As Boolean
    For Each line As String In lines
        If Line.Length > 0 Then
            sw.WriteLine (Line)
            ' Reset blank line flag
            foundBlank = False
        Else
            If Not foundBlank Then
                ' Blank line: write first one
                sw.WriteLine (Line)
                ' Set flag to indicate that blank line was found
                foundBlank = True
            End If
        End If
    Next
    sw.Close()
    fs.Close()
End If

[str_test]

You have a way of removing all of the blank lines from the array. Pass that array into this subroutine:

'PASS THIS SUBROUTINE YOUR ARRAY OF LINES WITHOUT ANY BLANK LINES
		'IN BETWEEN - THIS WILL ADD THE NECESSARY BLANK LINES
		Private Sub InsertBlankLines(ByRef passedLines() As String)
			Dim s As String = ""
			Dim blank As String = " "
			Dim count As Integer = passedLines.Length * 2
			Dim newLines(count) As String
			Dim i As Integer = 0
			For Each s In passedLines
				newLines(i) = s
				newLines(i + 1) = " "
				i = i + 2
			Next
			passedLines = newLines
		End Sub

This takes the passed array by reference, creates a new array twice the size as the original, cycles through all of the lines of the array placing blank lines in between the lines with text. By removing all blank lines in the array and then placing your own in you will not have to keep count of which lines are blank or not and/or which may or may not have had blank lines preceeding or following them.

Let me know if this helps...

[ansari]

you can loop until there is no extra 2 lines.

words="word1" & vbCrLf & vbCrLf & vbCrLf & vbCrLf & vbCrLf & vbCrLf & vbCrLf & vbCrLf & " word2"
strNewText = vbCrLf
strOldText = vbCrLf & vbCrLf
continueLoop=1
while continueLoop>0
continueLoop=instr(words,strOldText)
if continueLoop>0 then
words= Replace(words, strOldText, strNewText )
end if
wend

' output result replace vbCrLf with <BR/>
response.write replace(words,vbCrLf,"<BR/>")

the result will be :-

Word1
Word2

[JBourgeois]

No need for an array of Strings, which is very hard on resources. And no need to loop through all the lines.

There is a Replace command on the String class. Simply replace all the double CrLf by a single CrLf, looping until the size stops changing, something like

Dim length As Long
While length <> fileText.Length
    length = fileText.Length
    fileText = fileText.Replace(Environment.NewLine & Environment.NewLine, Environment.NewLine)
End While

Also note that although vbCrLf works, it is a good habit to use Environment.Newline instead.

vbCrLf exists only in VB. Environment.NewLine comes from the framework itself and can be used in any language. Also, Environment.NewLine is multiplatform, while vbCrLf works only in Windows.

By using Environment.NewLine, you write code that is more easily portable from one language to another. And you help yourself. If you ever have to program in another .NET language, the transition will be easier because you will have learned how to do things the .NET way, not only the VB way.

And this holds a lot of things, such as using MessageBox.Show instead of MsgBox; using String.Substring instead of Left, Right and Mid, etc.

I took that habit from the start in VB.NET, and god was I glad I had done so when I had to learn C#. I was already half in.

And while we are at it, give a look at what is in Environment. That class is a little treasure.