I've got ASP.NET intranet application written in VB. It gets a file from the user, and then depending on a few different cases it may create a few copies of the file as well as move the original.
Unfortunately I've come across a case where I get this error:
Exception Details: System.IO.IOException: The process cannot access the file
'\\some\dir\D09_03_5_180_0.000-6.788.png' because it is being used by
another process.
Which is thrown by My.Computer.FileSystem.CopyFile. And that's fine that it's being used by another process - it may still be saving/downloading from the user or trying to copy while another thread(?) is copying, I don't really care about that, what I want to know:
Is there any way that I can tell VB to wait to copy (also move) the file until the file is no longer in use?
Thanks
Test if the file is in use and the do what you need to do.
Public Sub WriteLogFile(ByVal pText As String, ByVal psPath As String, ByVal psName As String)
Dim strFullFileName As String
Dim Writer As System.IO.StreamWriter
Dim Fs As System.IO.FileStream
Try
Dim DirectoryHandler As New System.IO.DirectoryInfo(psPath)
strFullFileName = psPath & "\" & psName & Date.Today.Month.ToString & "-" & Date.Today.Day.ToString & "-" & Date.Today.Year.ToString & ".txt"
If Not DirectoryHandler.Exists() Then
Try
Monitor.Enter(fsLocker)
DirectoryHandler.Create()
Finally
Monitor.Exit(fsLocker)
End Try
End If
Try
If CheckIfFileIsInUse(strFullFileName) = True Then
Thread.Sleep(500) ' wait for .5 second
WriteLogFile(pText, psPath, psName)
If Not Fs Is Nothing Then Fs.Close()
If Not Writer Is Nothing Then Writer.Close()
Exit Sub
End If
Monitor.Enter(fsLocker)
Fs = New System.IO.FileStream(strFullFileName, IO.FileMode.Append, IO.FileAccess.Write, IO.FileShare.Write)
Writer = New System.IO.StreamWriter(Fs)
Writer.WriteLine(Date.Now.ToString & vbTab & "ProcessID: " & Process.GetCurrentProcess.Id.ToString() & vbTab & pText)
Writer.Close()
Fs.Close()
Finally
Monitor.Exit(fsLocker)
End Try
Catch ex As Exception
Dim evtEMailLog As System.Diagnostics.EventLog = New System.Diagnostics.EventLog()
evtEMailLog.Source = Process.GetCurrentProcess.ProcessName.ToString()
evtEMailLog.WriteEntry(ex.Message, System.Diagnostics.EventLogEntryType.Error)
Finally
If Not Fs Is Nothing Then Fs.Close()
If Not Writer Is Nothing Then Writer.Close()
End Try
End Sub
Public Function CheckIfFileIsInUse(ByVal sFile As String) As Boolean
If System.IO.File.Exists(sFile) Then
Try
Dim F As Short = FreeFile()
FileOpen(F, sFile, OpenMode.Append, OpenAccess.Write, OpenShare.Shared)
FileClose(F)
Catch
Return True
End Try
End If
End Function
Hmm... not directly.
What most implementations are doing, is making a retry of copying the file, with a small timeframe (some seconds)
if you want to make a nice UI, you check via Ajax, if the copying process went well.
Well, it turns out that waiting would not work in this case:
When trying to copy a file you cannot copy a file from one location to the same location or it will throw an error (apparently). Rather than just pretending to copy the file, VB actually tries to copy the file and fails because the copy operation is trying to copy to the file it's copying from (with overwrite:=True at least).
Whoops!
Related
I'm fairly familiar with bash, but I'm very, ***very**** new to vb.net. I'm searching for an easy way to find files in a folder that end with .G1, .G2, .G3, etc. but NOT .GP1, .GP2, .GP3, etc. Then for each file I need to copy it to another folder using a different file name but the same extension. I've managed to figure this out for the unique files, but there will be an undefined number of these depending on the project and I need to make sure that I get them all. Hard coding is possible, but very, very ugly. Any suggestions?
Here's the remnants of a failed attempt:
Public Sub FindGFiles()
FileList = IO.Directory.GetFiles(searchDir, ".G[1-99]" + , IO.SearchOption.AllDirectories)
For Each foundfile As String In FileList
If foundfile.Contains(".G#") Then
'copy file somehow and retain file extension
Else
MsgBox("No match")
End If
Next
End Sub
The GetFiles-method does only support * and ? wildcard characters.
So you have to get all files with a *.G*-extension first.
In the For Each-loop one can then use the Like-operator to check the desired pattern:
Public Sub CopyGFiles(searchDir As String, destDir As String)
Dim fileList As String() = IO.Directory.GetFiles(searchDir, "*.G*", IO.SearchOption.AllDirectories)
Dim fileName As String
Dim extension As String
For Each foundfile As String In fileList
fileName = IO.Path.GetFileNameWithoutExtension(foundfile)
extension = IO.Path.GetExtension(foundfile)
If extension Like ".G#" OrElse
extension Like ".G##" Then
'copy file to destination, append "_new" to the filename and retain file extension
IO.File.Copy(foundfile, IO.Path.Combine(destDir, fileName & "_new" & extension))
Else
'pattern not matched
End If
Next
End Sub
The method-call would then be as follows:
CopyGFiles("C:\Temp", "C:\Temp\Dest")
This should be done inside a Try/Catch as different exceptions can occur when working with files.
Try
CopyGFiles("C:\Temp", "C:\Temp\Dest")
Catch ex As Exception
MessageBox.Show("An error occured" + vbCrLf + ex.Message)
End Try
I get the feeling this is something really simple, but I've tried I don't know how many permutations of vbNewLine, Environment.NewLine, sMessage & vbNewLine (or Environment.Newline) I've tried, or how many pages on this site, or through Google I've looked at but nothing has worked.
I even tried getting help from a VB.Net discord channel I'm a part of and they suggested to do the same things that I've done and the procedure is still writing each new log entry at the end of the previous one in a continuous string. My writer is below. Am I missing something simple?
Edit: The code that worked is below in case anyone else comes along with the same issue. If you want to see the original code it's in the edit log.
Option Explicit On
Imports System.IO
Public Class WriteroLog
Public Shared Sub LogPrint(sMessage As String)
Dim AppPath As String = My.Application.Info.DirectoryPath
If File.Exists($"{AppPath}\Log.txt") = True Then
Try
Using objWriter As StreamWriter = File.AppendText($"{AppPath}\Log.Txt")
objWriter.WriteLine($"{Format(Now, "dd-MMM-yyyy HH:mm:ss")} – {sMessage}")
objWriter.Close()
End Using
Catch ex As Exception
MsgBox(ex)
Return
End Try
Else
Try
Using objWriter As StreamWriter = File.CreateText($"{AppPath}\Log.Txt")
objWriter.WriteLine($"{Format(Now, "dd-MMM-yyyy HH:mm:ss")} – {sMessage}")
objWriter.Close()
End Using
Catch ex As Exception
MsgBox(ex)
Return
End Try
End If
End Sub
End Class
The File.AppendText() method creates a new StreamWriter that is then used to append Text to the specified File.
Note, reading the Docs about this method, that you don't need to verify whether the File already exists: if it doesn't, the File is automatically created.
As a side note, when creating a Path, it's a good thing to use the Path.Combine method: it can prevent errors in the path definition and handles platform-specific formats.
Your code could be simplified as follows:
Public Shared Sub LogPrint(sMessage As String)
Dim filePath As String = Path.Combine(Application.StartupPath, "Log.Txt")
Try
Using writer As StreamWriter = File.AppendText(filePath)
writer.WriteLine($"{Date.Now.ToString("dd-MMM-yyyy HH:mm:ss")} – {sMessage}")
End Using
Catch ex As IOException
MsgBox(ex)
End Try
End Sub
The File.CreateText does not assign result to "objWrite", should be:
objWriter = File.CreateText($"{AppPath}\Log.Txt")
Not really sure if this is the root of your problem, but it is an issue.
In essences, your logic is re-opening or creating the stream "objWriter" for every call to this method. I would recommend you initialize "objWriter" to Nothing and only define if it is Nothing.
Set to Nothing as below.
Shared objWriter As IO.StreamWriter = Nothing
Then add check for Nothing in logic.
I am kicking off a number of instances of the same process and the issue is that they all write to the same log file. I know it is not a good practice and was wondering what can I do to avoid possible issues. Here is the procedure I use to write to file:
Sub WriteToErrorLog(ByVal Msg As String)
Dim path As String
path = System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location)
Dim strFile As String = System.IO.Path.Combine(path, "Log_" & DateTime.Today.ToString("dd-MMM-yyyy") & ".txt")
Dim sw As StreamWriter
Dim fs As FileStream = Nothing
Try
If (Not File.Exists(strFile)) Then
fs = File.Create(strFile)
fs.Close()
End If
sw = File.AppendText(strFile)
sw.WriteLine(Msg & vbcrlf)
Catch ex As Exception
MsgBox("Error Creating Log File")
MsgBox(ex.Message & " - " & ex.StackTrace)
Finally
sw.Close()
End Try
End Sub
I would appreciate any suggestions/improvements. thanks!
As I have said in my comment, the scenario of multiple access to the same file resource should be handled carefully and probably the best solution is to use a well tested log library like Log4Net or NLog.
In any case you could improve your code in a couple of point
Sub WriteToErrorLog(ByVal Msg As String)
Dim path As String
path = System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location)
Dim strFile As String = System.IO.Path.Combine(path, "Log_" & DateTime.Today.ToString("dd-MMM-yyyy") & ".txt")
Dim retry as Integer = 3 ' this could be changed if you experience a lot of collisions.'
Dim sw As StreamWriter = Nothing
While retry > 0
Try
Using sw = File.AppendText(strFile)
sw.WriteLine(Msg & vbcrlf)
End Using
Exit While
Catch ex as Exception
retry -= 1
End Try
End While
' If retry has reached zero then we have exausted our tentatives and give up....'
if retry = 0 Then
MessageBox.Show("Error writing to Log File")
End if
End Sub
I have removed all the part that check if file exists and then create it. This is not necessary because as the documentation explains, File.Append is the same that calling StreamWriter(file, true) and this means that if the file doesn't exist it will be created.
Next, to try to handle possible collision with other process writing to the same file concurrently, I have added a retry loop that could get access to the log file just after another process finishes.
(this is really a poor-man solution but then it is better to use a well tested library)
It is important to enclose the opening and writing of the file inside a using statement that closes and disposes the Stream also in case of exceptions. This is mandatory to be sure to leave the file always closed for the other processes to work.
I have a VB.NET program which lists some text files in a directory and loops through them. For each file, the program calls notepad.exe with the /p parameter and the filename to print the file, then copies the file to a history directory, sleeps for 5 seconds(to allow notepad to open and print), and finally deletes the original file.
What's happening is, instead of printing every single text file, it is only printing "random" files from the directory. Every single text file gets copied to the history directory and deleted from the original however, so I know that it is definitely listing all of the files and attempting to process each one. I've tried adding a call to Thread.Sleep for 5000 milliseconds, then changed it to 10000 milliseconds to be sure that the original file wasn't getting deleted before notepad grabbed it to print.
I'm more curious about what is actually happening than anything (a fix would be nice too!). I manually moved some of the files that did not print to the original directory, removing them from the history directory, and reran the program, where they DID print as they should, so I know it shouldn't be the files themselves, but something to do with the code.
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim f() As String = ListFiles("l:\", "997")
Dim i As Integer
Try
For i = 0 To f.Length - 1
If Not f(i) = "" Then
System.Diagnostics.Process.Start("Notepad.exe", " /p l:\" & f(i))
My.Computer.FileSystem.CopyFile("l:\" & f(i), "k:\" & f(i))
'Thread.Sleep(5000)
Thread.Sleep(10000)
My.Computer.FileSystem.DeleteFile("l:\" & f(i))
End If
Next
'Thread.Sleep(5000)
Thread.Sleep(10000)
Catch ex As Exception
End Try
End Sub
Public Function ListFiles(ByVal strFilePath As String, ByVal strFileFilter As String) As String()
'finds all files in the strFilePath variable and matches them to the strFileFilter variable
'adds to string array strFiles if filename matches filter
Dim i As Integer = 0
Dim strFileName As String
Dim strFiles(0) As String
Dim strExclude As String = ""
Dim pos As Integer = 0
Dim posinc As Integer = 0
strFileName = Dir(strFilePath)
Do While Len(strFileName) > 0
'check to see if filename matches filter
If InStr(strFileName, strFileFilter) Then
If InStr(strFileName, "997") Then
FileOpen(1, strFilePath & strFileName, OpenMode.Input)
Do Until EOF(1)
strExclude = InputString(1, LOF(1))
Loop
pos = InStr(UCase(strExclude), "MANIFEST")
posinc = posinc + pos
pos = InStr(UCase(strExclude), "INVOICE")
posinc = posinc + pos
FileClose(1)
Else : posinc = 1
End If
If posinc > 0 Then
'add file to array
ReDim Preserve strFiles(i)
strFiles(i) = strFileName
i += 1
Else
My.Computer.FileSystem.MoveFile("l:\" & strFileName, "k:\" & strFileName)
End If
'MsgBox(strFileName & " " & IO.File.GetLastWriteTime(strFileName).ToString)
pos = 0
posinc = 0
End If
'get the next file
strFileName = Dir()
Loop
Return strFiles
End Function
Brief overview of the code above. An automated program fills the "L:\" directory with text files, and this program needs to print out certain files with "997" in the filename (namely files with "997" in the filename and containing the text "INVOICE" or "MANIFEST"). The ListFiles function does exactly this, then back in the Form1_Load() sub it is supposed to print each file, copy it, and delete the original.
Something to note, this code is developed in Visual Studio 2013 on Windows 7. The machine that actually runs this program is still on Windows XP.
I can see a few issues. the first and most obvious is the error handling:
You have a Try.. Catch with no error handling. You may be running in to an error without knowing it!! Add some output here, so you know if that is the case.
The second issue is to do with the way you are handling Process classes.
Instead of just calling System.Diagnostics.Process.Start in a loop and sleeping you should use the inbuilt method of handling execution. You are also not disposing of anything, which makes me die a little inside.
Try something like
Using p As New System.Diagnostics.Process
p.Start("Notepad.exe", " /p l:\" & f(i))
p.WaitForExit()
End Using
With both of these changes in place you should not have any issues. If you do there should at least be errors for you to look at and provide here, if necessary.
I have the following code that I am using to parse out a test file. I am getting variable conversion error in Sub Main() when I assign file = Read(). The return value of Read() is a TextFieldParser type. How do I assign the proper variable type to "file" so I can write the output to a text file?
Thanks!
Module Module1
Function Read()
Using MyReader As New FileIO.TextFieldParser("C:\Users\Colin\Desktop\Parse_Me.txt")
Dim currentRow As String
While Not MyReader.EndOfData
Try
currentRow = MyReader.ReadLine()
Console.WriteLine(Parse_me(currentRow))
Catch ex As FileIO.MalformedLineException
MsgBox("Line " & ex.Message &
" is invalid. Skipping")
End Try
End While
Return MyReader
MyReader.Close()
End Using
End Function
Function Parse_me(ByVal test As String)
Dim Set_1, Set_2, Set_3, Set_4, Set_5 As String
Dim new_string As String
Set_1 = test.Substring(0, 4)
Set_2 = test.Substring(7, 2)
Set_3 = test.Substring(11, 1)
Set_4 = test.Substring(14, 4)
Set_5 = test.Substring(20, 4)
new_string = Set_1 & " " & Set_2 & " " & Set_3 & " " & Set_4 & " " & Set_5
Return new_string
End Function
Sub Main()
Dim file As Object
file = Read()
FilePutObject("C:\Users\Colin\Desktop\Parse_Meoutput.txt", file)
End Sub
End Module
Here's how FilePutObject is supposed to work (example taken from MSDN documentation for FilePutObject):
Sub WriteData()
Dim text As String = "test"
FileOpen(1, "test.bin", OpenMode.Binary)
FilePutObject(1, text)
FileClose(1)
End Sub
The 1 act as an identifier for the file. Note also that the file name is passed to FileOpen before calling FilePutObject, and that FileClose is called afterwards. Also note that a string is being written to the file. I don't know which types of data are valid for being passed to FilePutObject, but FileIO.TextFieldParser is definitely not one of them (I just tried it).
Correct me if I'm wrong, but I'm pretty sure that FilePutObject is one of those carry-overs from VB6. If you're writing new code, I would rather use a Stream object for my I/O. For one, it's a lot more .Net-ish (i.e., type-safe, object-oriented, etc). And as far as usability goes, it's a lot clearer how a Stream works, not to mention it doesn't involve passing arbitrary integers as handles to functions in order to identify which file you'd like to work with. And to top it all off, a Stream works whether you want to write to a file, to the console, or send the data to another machine. To sum up, I would definitely look up the Stream class, some of its child classes (like FileStream, and whatever else appeals to you), and some associated types (such as the TextWriter class for conveniently writing text).
Change the definition of the function "read" to:
Function Read() as FileIO.TextFieldParser
and change the declaration of "file" in sub main to:
Dim file as FileIO.TextFieldParser
That way the data type of the function and assignment match.