.net - Inter Process Reader Writer Lock (or File Handles And Access Denied)
May 8, 2009
We needed an inter-process reader/writer lock.We decided to use a file and lock the first byte using LockEx and UnlockEx. The class creates a file in the system temp folder when it is created. The file is created with readwrite access and share read|write|delete.We also specify DeleteOnClose so we don't leave loads of temp files laying around. Obviously AcquireReader and AcquireWriter call LockEx with appropriate flags and ReleaseLock calls UnlockEx.We have tested this class using a small application that you can run several instances of and it works perfectly. The application that uses it has a problem, which we have managed to re-produce in another small test app. In pseudo code it is
Create InterProcessReaderWriter
Dispose InterProcessReaderWriter without acquiring any locks
Launch a child process which takes a reader lock
The first time this runs, it works fine. If you attempt to run it again, while the child process from the first time is still holding the lock, we get an UnauthorisedAccessException when trying to open the file.This appears to be a permission issue, not a sharing violation but all the processes in this test case are running as the same user.
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Jan 24, 2012
1. I have to create a file. 2. Then I want to write a string into the text file.
I can do part 1 no problem with: File.Create(strFilePath) But when I try part 2 to write to the file it won't allow this as it's still being used:
sw = File.AppendText(strFileName)
sw.WriteLine(strCode)
sw.Flush()
sw.Close()
My code in part 2 works fine on a file that hasn't just been created.
How do I release the file from the File object?
There doesn't seem to be a .close or .flush option.
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Jan 27, 2009
I am trying to make my application read data from a file. Then save the data back. However I keep getting an error which says the file is still open so cannot be edited. I also read that there is an issue with the streamreader and streamwriter do not close the program straight away. I was wondering if anyone had a way around this or any alternative ideas. Heres my code so far!
[Code]...
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Sep 29, 2010
I am getting the below error when I click a row in the grid. But this error is raised only in exe, which is installed in client machine, but when I check the same from source code in my machine, i am not getting this error. I am able to locate the record.
[Code]...
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Sep 11, 2009
i am working on a project that uses an magnatec card reader mse-750 iam facing a problem in making the machine on read mode so i can read from it iam using vb.net?
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May 25, 2009
this project im working on is giving me a headache. am trying to write a program to recognie both ntfs and ext3 fileformats and enable the copying of files between them. ive done the ntfs bit and my problem is how do i implement the ext3 file system reader and writer using visual basic.net.any references would be really useful.
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Apr 30, 2009
The bigger problem is that I can't seem to get everything involving using stream writer and reader working. If I start of with a .txt file already correctly formatted then I can display it in the list box. But adding data during run time is not proving successful.
[Code]....
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Jan 20, 2012
How do I get the list of open file handles by process id in C#?
I'm interested in digging down and getting the file names as well.
Looking for the programmatic equivalent of what process explorer does.
Most likely this will require interop.
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Apr 28, 2011
I'm trying to setup a simple app that reads a file and then writes the contents to another file using OpenFileDialog and SaveFileDialog. Looking at the debbugger it looks like it's reading fine, I can see the data I want written. Towards the end of my code I get the following error message:"Illegal characters in path". I've researched this error. I'm not using any illegal characters such as /\? etc and the pathname contains all alpha characters. I'm pulling the test file from the C drive and trying to save it there as well.
Path: C:\Test.csv
My code:
Private Sub btnAppendData_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAppendData.Click
Dim Result As DialogResult
Dim FileContents As String
[Code] .....
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Apr 28, 2009
I am new to Visual Basics and I am using Visual Basic 2008 express. I have been using video tutorial on line to learn VB and they are great in explaining what is happening the code vs. just looking at code. I think from what little I can find I would be using StreamWriter WriteLine and StreamReader readLine .I am using a couple of forms. I am looking for simple basic code to use a form as a way of modifying timer intervals and store the values in a single text file on separate lines.
Description:
Form1: will contain the main code that will run. It will contain some timers. I want the timers to look in a text file for their intervals. Each timer would be on a different line.
Example:
Timer1 interval would be located on line 3
Timer2 interval would be located on line 6
Timer3 interval would be located on line 20
Form2: will contain 3 textboxes. This is where when I load form2 I will also read the same values from the text file to preload the text boxes. I will now be able to change the timer intervals as needed and press a button to update the text file. The update button will also reload the new timer settings on Form1. This is very similar to how a CNC Machine works with Parameter settings. This can be useful for storing many different settings for a form that a user can modify and be stored and reloaded next time the program runs.
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Oct 19, 2010
I'm making a browser and for the favorites I'm using a reader and writer to read and write new favorite to a .txt file. Now if I edit the text file manually and load up the browser, the favorites show up as they should but the problem comes in when I add the a new favourite and then reload the application. Once reloaded the favorites seem to copy what was originally in the file and then whatever I added last at the bottom.
Here is the
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
WebBrowser1.Navigate(TextBox1.Text)
ListBox1.Items.Add(TextBox1.Text)
[Code] .....
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Dec 6, 2010
I have a program that reads a text file tab delimted using OLEDb .I need to be able to allow the user to insert a user created record into the file which I can do.
The problem is I need to be able to let the user edit that record. From my understanding you can not edit or delete with OLEDB only insert So I thought I would read the file using stream reader, find the line I want to edit and just delete it, rewrite the file, then let the user insert a new record
If someone has a better way to perform this operation I am open its just the best way I could find with my limited knowledge and the reading and researching I have been doing thus far.
So I am trying to step-by step and first read the file which seems to work then find the line that would need to be deleted. So I was trying to use the
line.startswith method. I am using msgbox to see if that works before I continue but it doesnt seem to work I know my file has several lines starting with "Active" but my msgbox returns "False"
Here is the code I have so far
[code...]
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Aug 6, 2009
I have a smart card reader/writer hooked up to my serial port. i've already coded the program to give access to the serial port. How would I go about getting my Card Reader/writer recognized in my program. I basically want to click the "read button" and whatever is on the current smart card im trying to read, pop up on the screen.
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Aug 18, 2011
I'm building a tool that consists of a Webservice that will run commandline tools at specific times. On average there will be running 15-20 CL tools at the same time. Every CL tool runs no longer than about 0,5-1 minute on average. The webservice needs to be able to check each CL's status every 2-3 seconds or so.
I've got some advice about how to do this; named pipes looks likes the best "technical" solution. However I'm wondering if communicating with simple very small text "status" files would be a better, less complicated and less error-risk, way. I prefer the solution that is the most resource friendly.
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Apr 13, 2012
I have 2 applications that needs to talk to each others. After some research, I wanted to go with managed pipe (namespace system.io.pipes). The problem is, the client must send commands to the server but need to also wait for incoming message from the server at the same time. I tried to go asynchrone but it doesn't work.
[Code]...
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Oct 13, 2009
I am having a problem with this:
Dim ProcessList() As Process = Process.GetProcessesIf ProcessList.Length > 0 Then Dim ProcessListIdx As Integer For ProcessListIdx = 0 To ProcessList.Length - 1 If Not ProcessList(ProcessListIdx).HasExited Then <-- this line throws the error With
[code].....
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May 31, 2012
I thought I postet this yesterday but I can't find my thread so if this is a duplicate please point me at the original one. Background: I need to create a user account and Modify it's registry before the user logs on the first time. Creating the account is done by using the Winnt provider (works great). To create the profile I'm trying to use Process.start to launch a process as the newly created user. With the use of loaduserprofile property the users profile gets created and i can do my regwrites without problem.
[Code]...
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Aug 25, 2011
ran into an issue but i have no idea why. I made a program that reads in a text file. I tested the program and it worked perfectly. I made the setup file using the setup wizard, installed the program on my computer and tried to test it and it gave me anerror about not being able to access the text file. I attempted to run the program right in VS because it had worked fine before and now even in that i am getting an error saying it cant access the text file. I dont know why it did work and now suddenly it
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Dec 15, 2009
I have written a simple module to access NTFS Alternate Data Streams (ADS), which looks like this:
Imports System.IO
Module Module_ADS ' Alternate Data Streams
Private Const GENERIC_ALL As Int32 = &H10000000
[code]....
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Jun 21, 2010
Using the following sub to download a file I receive an "Access to the path 'path' is denied" no matter where I try to download it to even if I run the program as an administrator.Why do I get an access denied error?
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
MsgBox("HLDSUpdateTool is Copyright © VALVe Corporation. We are not affiliated with VALVe Corporation in any way.", MsgBoxStyle.Exclamation, "Copyright")
[code]....
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Nov 28, 2011
The Program Connects and Download the File, but when it writes it to the Disk i get an Access Denied Error. on Using Fs as new.Im Running full System admin, Not sure why it is giving this error. Heres the code where it all gose wrong:
Dim rfn As String = "FTP FILE"
Dim lfn As String = "LOCAL LOCATION"
Dim ftp As FtpWebRequest = CType(FtpWebRequest.Create(RFN), FtpWebRequest)
[code].....
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Apr 17, 2012
I am using net 2010 net framework 2 & w7 In windows explorer I want to move or rename a file but I get a windows message with a heading "File Access Denied" you need administrator permission to do this In my vb code I want to move the same file but get an error, the security on the file is "Read & execute" and "Read" How do I detect this before the code for moving & also set the permissions so I can move it with vb code.
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Aug 22, 2011
I try to map to the network drives and i am able to read the number of folders in the drives and access right for FULL CONTROL ( READ , write etc. ) is given to me and in fact "everyone in the same domain group that i am in. However i encounter the following code error where FileOpen(1, ReadString, OpenMode.Binary) --> It prompts that access to the path of \xxxxxxxxxfolder is denied.
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Mar 28, 2012
I am trying to have my program stop a process then delete the file (the process file)
Dim pProcess() As Process = System.Diagnostics.Process.GetProcessesByName("Bit")
For Each p As Process In pProcess
p.Kill()
Next
[code]....
Everything works perfectly fine untill the kill file command (i have tried file.delete, and My.Computer.FileSystem.DeleteFile to try to delete the file) but in all attempts i get a "Access to the path "(pathHere)" is denied.
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Jun 27, 2011
I'm having trouble reading a file into a filestream from a CD. I get 'Access to the path denied'. Works fine when reading a text file from a local drive, but getting error from CD. Dim fs As New IO.FileStream(filename, IO.FileMode.Open)
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Mar 30, 2009
Dim strCRLocalPath As String = "c:CR"
Dim strDestinationFile As String = strCRLocalPath & strFileName
If Dir(strCRLocalPath) = "" Then MkDir(strCRLocalPath)
FileCopy(strSourceFile, strDestinationFile)
how to correct it? Error message: "Path/File access denied"
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Feb 17, 2012
I have difficulty in removing the LDB generated by the "CREATE" method of ADOX in the following code segment.Aims: Create (on the fly) a new access database and then export data (says Arena modules) to that newly created database.
Expected: The newly created access database should be able to be used by some external operations, say Access.exe, after the end of the subroutine and without exiting the current VB program.
1) I tested that the "Arena code" do nothing about the create/release of the ldb file.
2) I tested the "Exclusive Mode" in connection string, but the access file is still locked by the vb program.
3) I tested under both inside the VB environment, and directly invoke the generated from Explorer, and same results.
4) Other database formats is not the options to me. (due to Arena export limit)
5) It is not a web app.
Code:
Sub Method1()
Dim logs As New System.Collections.Generic.List(Of String)
Dim arenaApp As Arena.Application = Nothing
Try
[code]....
Platform:
Windows 7 64bit, Office 2010 (32)
VB 2010 express
Lib: MS ADO Ext. 2.8 for DDL and Security
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Apr 10, 2010
I tired this [code]...
but this code not working on windows vista, i can use it on windows xp, i think problem is user permissions but i have to delete or create file via my application how can resolve this problem.
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May 17, 2012
Imports System.IO
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
[Code].....
but alwys i get thie error access to the path e: is denied but the hard drive is accessable, so how i copy a fil from resource to a a disk drive like F: /
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Apr 19, 2010
I'm trying to run an EXE file using process.start.I've put in username, password and domain that it is accepting (it complains when I put the wrong password, and not when I put the right one, so it is checking etc), and that have local admin rights on the PC.However, when I try to run an EXE that's stored in Program Files, I cannot run it. It always says Access is Denied. When I copy that EXE to another folder, it runs perfectly![code]
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