I am reading very large text files (6-10 MB). I am splitting the text files in to multiple new text files. There is common "header" and "footer" in the "read" text file that I will store as variable to be called at later time. I can't figure out how to properly dispose of IO.File.ReadAllLines. I'm concerned this will be held in memory if I don't dispose of it properly.
Text.Dispose or Text.Close isn't valid.
Dim testHeader As String
Dim testSite As String
Dim testStart As String
Dim testStop As String
Dim testTime As String
Dim text() As String = IO.File.ReadAllLines("C:\Users\anobis\Desktop\temp.txt")
testHeader = text(0)
testSite = text(text.Length - 4)
testStart = text(text.Length - 3)
testStop = text(text.Length - 2)
testTime = text(text.Length - 1)
text.dispose()
Later in the program I will be initiating another StreamReader and want to avoid conflicts and memory resource issues. I am new at coding so be gentle! Thanks!
' Open temp.txt with "Using" statement.
Using r As StreamReader = New StreamReader("C:\Users\anobis\Desktop\temp.txt")
' Store contents in this String.
Dim line As String
line = r.ReadLine
' Loop over each line in file, While list is Not Nothing.
Do While (Not line Is Nothing)
If line Like (sourceSN.Text + "*") Then 'Substitute in source serial number "xxxxxx*"
file.WriteLine(line)
End If
' Read in the next line of text file.
line = r.ReadLine
Loop
End Using
file.WriteLine(testSite)
file.WriteLine(testStart)
file.WriteLine(testStop)
file.WriteLine(testTime)
' Close transfer.txt file
file.Close()
You don't need to dispose of it. It returns a managed string array, who's lifetime is managed by the garbage collector. Internally, File.ReadAllLines is disposing of the underlying native file handle it created to read all of the lines for you.
Related
I am a student in computer science and for a project I need to be able to read from a text file in a way that each line is assigned to a space within an array. This should happen so that each line of text file is read in the order that it appears in the text file. I would also appreciate any methods of writing to a text file as well.
If this question is already explained, could you please direct me to the existing answer.
Things to note:
1) I am coding in a console application in VB.NET
2) I am relatively new at coding
You can do it like this:
Dim sFile As String = "D:\File.txt"
Dim aLines As String() = System.IO.File.ReadAllLines(sFile)
System.IO.File.WriteAllLines(sFile, aLines)
Here's a sample from the official documentation:
Imports System.IO
Public Class Test
Public Shared Sub Main()
Dim path As String = "c:\temp\MyTest.txt"
Dim sw As StreamWriter
' This text is added only once to the file.
If File.Exists(path) = False Then
' Create a file to write to.
Dim createText() As String = {"Hello", "And", "Welcome"}
File.WriteAllLines(path, createText)
End If
' This text is always added, making the file longer over time
' if it is not deleted.
Dim appendText As String = "This is extra text" + Environment.NewLine
File.AppendAllText(path, appendText)
' Open the file to read from.
Dim readText() As String = File.ReadAllLines(path)
Dim s As String
For Each s In readText
Console.WriteLine(s)
Next
End Sub
End Class
Remarks
This method opens a file, reads each line of the file, then adds each line as an element of a string array. It then closes the file. A line is defined as a sequence of characters followed by a carriage return ('\r'), a line feed ('\n'), or a carriage return immediately followed by a line feed. The resulting string does not contain the terminating carriage return and/or line feed.
Module Module1
Sub Main()
'Declare four variables
Dim oReader As New System.IO.StreamReader(".\archive01.txt") 'This file has to exist in the aplication current directory.
Dim oWriter As New System.IO.StreamWriter(".\archive02.txt") 'This file will be created by the software.
Dim oArray() As String = {}
Dim oString As String = Nothing
'For reading from .\archive01.txt and to load in oArray().
oString = oReader.ReadLine
While Not oString Is Nothing
If UBound(oArray) = -1 Then 'Ubound = Upper Bound, also exist LBound = Lower Bound.
ReDim oArray(UBound(oArray) + 1)
Else
ReDim Preserve oArray(UBound(oArray) + 1)
End If
oArray(UBound(oArray)) = New String(oString)
oString = oReader.ReadLine
End While
oReader.Close()
'For writing from oArray() to .\archive02.txt.
For i = 0 To oArray.Count - 1 Step 1
oWriter.WriteLine(oArray(i))
Next
oWriter.Close()
End Sub
End Module
Hi, try with this code. It works well. I hope that this helps to you to learn how to do this kind of things. Thank you very much. And happy codding!. :)
Im trying to output the data from the second line of my textfile to a datagridview but when doing so it is also outputting every line after the the second line. This is what I have tried. Thanks
Dim lines = IO.File.ReadAllLines(OrderID & ".txt")
For index = 1 To lines.Length - 1
Dim cells = lines(index).Split(","c)
dgvOutput.Rows.Add(cells)
FileClose()
It's outputting every line after the second line, because that's what you're telling it to do when you iterate through the array of strings returns from ReadAllLines.
IO.File.ReadAllLines does not leave an output stream open. The file is closed. What it does do, is return a zero-based (by default) array of the contents of the file, with line breaks being the delimiter for the split.
To just get the contents of the second line, using ReadAllLines, this is what you need:
Dim lines = IO.File.ReadAllLines(OrderID & ".txt")
If lines.length >= 2 Then
Dim cells = lines(1).Split(","c)
dgvOutput.Rows.Add(cells)
End If
Now, that does have the overhead of reading the entire file in. If you open the file using a reader object, then you only need to read the first and second lines of the file to get that second line.
That would be something like this:
Dim reader as StreamReader = My.Computer.FileSystem.OpenTextFileReader(OrderId & ".txt")
Dim a as String
' This reads the first line, which we throw away
reader.ReadLine()
a = reader.ReadLine()
reader.Close()
Dim cells = a.Split(","c)
dgvOutput.Rows.Add(cells)
You would need to test your explicit circumstances to determine which is better for what you're trying to do.
Your loop is executed over all lines skipping just the first line.
While I cannot see what happen in the FileClose call it seems to not have any sense because ReadAllLines has already closed the file.
You can get the second line of your file with a single line of code
Dim line as String = File.ReadLines(OrderID & ".txt").Skip(1).Take(1).FirstOrDefault()
' this check is required to avoid problems with files containing 0 or 1 line
if line IsNot Nothing Then
Dim cells = line.Split(","c)
dgvOutput.Rows.Add(cells)
End If
Notice that I have replaced the ReadAllLines with ReadLines. This is better because using this method you don't read all lines when you need only the second one (if it exists). More info at ReadLines vs ReadAllLines
Dim lines = IO.File.ReadAllLines(OrderID & ".txt")
Dim SecondLine = lines(1)
File.ReadAllLines opens and closes the file for you so there is not need to add code to close it.
I am currently trying to manipulate a line in a file that we are using to retain data, using comma delimiters. For example -
121,1212, XJAY,Sean K,Kean S,AAAA-BBBB-AAAA-BBBB-AAAA
12456,987654,WYST,Steve Jobs,Bill Gates,CAAA-BBBB-AAAA-BBBB-AAAA
If I assume that the last line is always a unique code, is it possible to identify that line in the text file and append it with another field?
Prior research has been reading through the APIs for StreamReader and StreamWriter, and looking through other StackOverflow questions, however most questions seem focused on just appending to the end of the file, or in different languages!
As always thank you for your time, and if there is anything I've left off please let me know!
You can't manipulate a line in a file in any reasonably easy way.
There are no methods to work with lines in a file, because files are not line based. They are not even character based. The bytes in the file are decoded into characters, then the line break characters are recognised and the characters can be split into lines.
The easiest way to manipulate a line is to read the entire file into a string array, change the string that you want change, then write the entire string array to the file.
Example:
Dim fileName As String = "c:\data.txt"
Dim lines As String() = File.ReadAllLines(fileName)
For i As Integer = 0 To lines.Length - 1
Dim line As String = lines(i)
If line.StartsWith("12456,") Then
lines(i) = line & ",More data"
End If
Next
File.WriteAllLines(fileName, lines)
If you are looking for a way to parse Each line with StreamReader and StreamWriter: Here it is:
'You will need Imports System.IO
Dim TheNewFile As String
Dim MyLine As String
Dim MyStream2 As New FileStream("C:\Your Directory\YourFile.txt", FileMode.Open)
Dim MyReader As New StreamReader(MyStream2)
Dim MySettings As New StringReader(MyReader.ReadToEnd)
MyReader.BaseStream.Seek(0, SeekOrigin.Begin)
MyReader.Close()
MyStream2.Close()
Try
Do
MyLine = MySettings.ReadLine
'This if statement is an exit parameter. It can be if it contains or if 5 consecutive lines are nothing. It could be a number of things
If MyLine Is Nothing Then Exit Do
'This is the file you will write. You could do if MyLine = "Test" Then ........... append whatever and however you need to
TheNewFile = TheNewFile & MyLine & vbCrLf
Loop
Catch ex As Exception
MsgBox(ex.ToString())
End Try
'-----------------Write The new file!!!----------------
Dim MyStream3 As New FileStream("C:\Where you want to write New File\NewFileName.txt", FileMode.Create)
Dim MyWriter3 As New StreamWriter(MyStream3)
MyWriter3.Write(TheNewFile & "Test")
MyWriter3.Close()
MyStream3.Close()
I am working on a utility that will take the contents of a .ps1 script (Powershell), and run it in the context of a VB.NET Winform. Basically it does this by referencing some Powershell DLLs, opening the .ps1 file, reading a line of text and feeding it into an internal string that will run on a button click event.
Here's the full code I have so far:
Private Function RunScript(ByVal scriptText As String) As String
' create Powershell runspace
Dim MyRunSpace As Runspace = RunspaceFactory.CreateRunspace()
' open it
MyRunSpace.Open()
' create a pipeline and feed it the script text
Dim MyPipeline As Pipeline = MyRunSpace.CreatePipeline()
MyPipeline.Commands.AddScript(scriptText)
' add an extra command to transform the script output objects into nicely formatted strings
' remove this line to get the actual objects that the script returns. For example, the script
' "Get-Process" returns a collection of System.Diagnostics.Process instances.
MyPipeline.Commands.Add("Out-String")
' execute the script
Dim results As Collection(Of PSObject) = MyPipeline.Invoke()
' close the runspace
MyRunSpace.Close()
' convert the script result into a single string
Dim MyStringBuilder As New StringBuilder()
For Each obj As PSObject In results
MyStringBuilder.AppendLine(obj.ToString())
Next
' return the results of the script that has
' now been converted to text
Return MyStringBuilder.ToString()
End Function
' helper method that takes your script path, loads up the script
' into a variable, and passes the variable to the RunScript method
' that will then execute the contents
Private Function LoadScript(ByVal filename As String) As String
Try
' Create an instance of StreamReader to read from our file.
' The using statement also closes the StreamReader.
Dim sr As New StreamReader(filename)
' use a string builder to get all our lines from the file
Dim fileContents As New StringBuilder()
' string to hold the current line
Dim curLine As String = ""
' loop through our file and read each line into our
' stringbuilder as we go along
Do
' read each line and MAKE SURE YOU ADD BACK THE
' LINEFEED THAT IT THE ReadLine() METHOD STRIPS OFF
curLine = sr.ReadLine()
If curLine.Contains("") Then
fileContents.AppendLine("$Folder=tbpath.selectedpath")
Else
fileContents.Append(curLine + vbCrLf)
If curLine.Contains ($Folder="") Then
Loop Until curLine Is Nothing
' close our reader now that we are done
sr.Close()
' call RunScript and pass in our file contents
' converted to a string
Return fileContents.ToString()
Sorry for the lengthy stuff, but the lines I am curious about are the curLine.Contains part. What I'm trying to do is have the parser detect whether or not the line is a specific one (which reads $Folder = "") and replace the empty quotes with a folder path that is stored in a text box (tbpath.selectedtext). Unfortunately, since the Powershell script requires quotes around the path string (in case there are spaces) I am having trouble figuring out how to do what I want it to do.
What should I do there? Should I build what I want into a new variable (maybe vbPath = tbpath.selectedtext) and put it into the new line? Are there any "best practices"?
Double up the quotes
Dim s As String = "$Folder = """""
s =
$Folder = ""
In your code
If curLine.Contains("$Folder = """"") Then
End If
Do you want curLine.Contains() to check for a literal string $Folder=""? If so, you need to put the whole string in double quotes and escape the inner ones. Double quotes are escaped by doubling them. Also, if you want to insert a variable, you need to concatenate it with the string literals, so the command should probably look like this:
If curLine.Contains ("$Folder = """"") Then
fileContents.Append("$Folder = """ & tbpath.selectedpath & """")
End If
I'm having a problem where instead of reading a text file from the location string, I changed it to read the text file from the resource location and it breaks my program. I've also used the insert snippet method to get most of this code, so it is safe to say I don't know what is going on. Could some one please help?
'reads the text out of a delimited text file and puts the words and hints into to separate arrays
' this works and made the program run
' Dim filename As String = Application.StartupPath + "\ProggramingList.txt"
'this dosnt work and brings back a Illegal characters in path error.
dim filename as string = My.Resources.ProggramingList
Dim fields As String()
'my text files are delimited
Dim delimiter As String = ","
Using parser As New TextFieldParser(filename)
parser.SetDelimiters(delimiter)
While Not parser.EndOfData
' Read in the fields for the current line
fields = parser.ReadFields()
' Add code here to use data in fields variable.
'put the result into two arrays (the fields are the arrays im talking about). one holds the words, and one holds the corresponding hint
Programingwords(counter) = Strings.UCase(fields(0))
counter += 1
'this is where the hint is at
Programingwords(counter) = (fields(1))
counter += 1
End While
End Using
the error
ex.ToString()
"System.ArgumentException: Illegal characters in path.
at System.IO.Path.CheckInvalidPathChars(String path)
at System.IO.Path.NormalizePathFast(String path, Boolean fullCheck)
at System.IO.Path.NormalizePath(String path, Boolean fullCheck)
at System.IO.Path.GetFullPathInternal(String path)
at System.IO.Path.GetFullPath(String path)
at Microsoft.VisualBasic.FileIO.FileSystem.NormalizePath(String Path)
at Microsoft.VisualBasic.FileIO.TextFieldParser.ValidatePath(String path)
at Microsoft.VisualBasic.FileIO.TextFieldParser.InitializeFromPath(String path, Encoding defaultEncoding, Boolean detectEncoding)
at Microsoft.VisualBasic.FileIO.TextFieldParser..ctor(String path)
at HangMan.Form1.GetWords() in I:\vb\HangMan\HangMan\Form1.vb:line 274" String
The TextFieldParser constructor you use expects the name of a file. Instead, it gets the contents of the file. That goes Kaboom, the file content is not a valid path to a file. You'll need to the constructor that takes a Stream and use the StringReader class to provide the stream. For example:
Dim fields As String()
Dim delimiter As String = ","
Dim fileContent As String = My.Resources.ProggramingList
Dim stringStream as New System.IO.StringReader(fileContent)
Using parser As New TextFieldParser(stringStream)
REM etc...
End Using
This is a bit wasteful of memory but not an issue if the text is less than a megabyte or so. If it is more then you shouldn't put it in a resource.
When you debug this code, what is the value of the variable filename after you read it from My.Resources.GamesList? Is it a valid string, does it point to you're file?