Handle Concurrent File Access With A Filestream/streamwriter?
Dec 10, 2009
I am writing an audit file that is writing the username, time, and the old/changed values of several variables in the application for each user when they use my application. It is using a FileStream and StreamWriter to access the audit file. All audits for each user will be written to the same file. The issue is that when two users are updating this audit file at the same time, the "old value" of each of the variable is mixing up between the users.
Dim fs As FileStream
Dim w As StreamWriter
Public Sub WriteAudit(ByVal filename As String, ByVal username As String, ByVal oldAddress As String, ByVal newAddress As String, ByVal oldCity As String, ByVal newCity As String)
[code]....
This lives in an AuditLogger class, which is referenced via an instance variable (re-allocated each time the function is accessed).
I am trying to use filestream and streamwriter / streamreader to have a simple text box where the text entered is written to a text file, and then a button can be clicked to read the file and present the text back to the textbox. It works, but the problem I'm having is that if i change the text to something smaller in length (less text) than what is currently in the file, then press the button to read the file, it still contains some of the old text that was previously in the file.
Dim strmReadFile As New FileStream(txtPath.Text, FileMode.Open, FileAccess.Read, FileShare.Read) Dim readHandle As New StreamReader(strmReadFile) 'read the entire text, and set it to a string Dim streamFileContents As String = readHandle.ReadToEnd()
I have written some simple codes which are using FileStream to read a big .zip file.My codes ran fine as expected until I tested to create multiple threads to access that particular same .zip file at the same time.
The error that I've got was > The process cannot access the file 'D: est.zip' because it is being used by another process.Is it possible to read 1 particular file by multiple FileStream instances at the same time?
The goal is to write data to a SQL Server 2008 FILESTREAM file using VB.Net. An "Access Denied" message occurs when creating a FileStream object in the code(see red underlined code below). SQL Server 2008 is configured to "Allow remote clients to have streaming access to FILESTREM data" along with "Enable FILESTREAM for Transaction-SQL access"... What configuration setting is missing and causing the "Access Denied" message? Figure 1.) Code used to stream data to SQL Server managed file
I have trouble accessing filestream via SqlFileStream. Sql server and IIS7 are on different servers, remote access to Filestream is enabled. Workgroup for both servers is the same.I've tried everything, including opening user with identical username/passwords on both servers. Didn't work. Dim sqlFileStream As New SqlTypes.SqlFileStream(filePath, txContext, IO.FileAccess.Read)I have both filePath and context.However, when I open server via explorer logged on locally as Administrator, I also get access denied if I try to acesss this share.Can permissions for this share be edited at all?
I have implemented the filestream feature of SQL Server 2008 in a VB.Net application. I can insert files, and then retrieve/view them just fine. However, I have huge problems trying to update a file. Eg. The user selects a file from the grid which I execute via process.start. If that file is a .txt file, the user may choose to edit it. In case that happens, I need to save the changed file back to the database. So far I have failed to do that.
What I do, is take the retrieved file, copy it (cause i got some errors about it being used), and then Process.Start it. After that, via .NET filestream, I convert the file to bytes and try to update the record. SQL Profiler and a manual SELECT on the varbinary(max) column tell me that the file is updated properly, but the very next try to retrieve it I get an unchanged file.
After that I also tried to update the file by changing its File-System Version, but the file still wouldn't seem to update. Does Anyone have a code sample of how I can achieve this operation? Like 500 sites on the internet have examples of how to Insert And Retrieve the file, but not a single example on how to update. This is how my second attempt of trying to update the file via the filesystem looks like. The code for inserting/retrieving is very similar and it works properly. [Code]
I've seen a lot of threads in respect to file access denial, but haven't really found one that suited my particular issue. In my application the part that's not permitting the file to be saved is in the below code. I have 21 text boxes that I'm writing to a file that when in the developmental environment (Visual Studio 2010) works just fine however, when I create a setup program and then install it to a directory I get the infamous "Access to the path 'C:Program Files (x86)Blah, blah' umbers.dat is denied." before uninstalling it I took a look at the permissions on the file itself and ReadOnly is not the issue. I tried looking at the FileIOPermission Class, but find anything that would work for me or perhaps I was doing something wrong. [code]
I am taking in two html files and creating one out of them. To do this I am opening the first html file and not writing out the closing </body> and </html> tag and opening the second file and not writing out the corresponding opening tags, as well as the <style></style>section. I start a streamwriter, and write the lines out to it, and then close the streamwriter. My problem is that the output file is filled with strange characters. I've tried opening the streamwriter with different character sets as the third parm, but all this does is change the characters to different strange characters.It says charset=windows-1252 at the tops of the input files (and the output files for that matter - since I'm just reading stuff in and writing it out - with the exceptions mentioned above).Questions;First, do you think I am properly approaching appending two .htm files together?Second, how can I eliminate these strange characters.
I have found many pages referring to having the date be part of a txt file being created, but not like the way I need. Having said that, this is what I've got.. [code] I read a page on working with txt files and learned what I could from it. It said to use the method in the beginning of my code for creating the file. It works great, but I would like to have a new file name everday, hence the date being integrated. So even if program was running, when midnight hits, a new txt file is created and new entries are written to that file. But I can't even get the date to be put in there. Everytime I try to make this work by using methods I read about in other pages, I get a syntax error, or a warning saying an end of statement is expected. I'm not sure those methods are compatible with what I've already got going.I was actually trying to store these values in a database, and I got real close I think, but I couldn't get any help to fix my problem so I'm trying to write to daily txt files instead. url....
I have a filestream, and I want to save a file from that filestream? Like there are bytes in that file stream, and from those I want a "file.exe" to automatically appear on my desktop.
I'm using a code snippet, and I think this is the important part: Dim fstr As New FileStream("file.exe", FileMode.OpenOrCreate, FileAccess.Write) fstr.Write(validArg1, validArg2, validArg3) fstr.Close()
Do I have to use a for loop? Or is there a function like this: IO.File.WriteAllBytes(myPath, fstr.AllBytes)
Here's the catch - for the program I'm making I would like to avoid creating a copy of the file in its totally unencrypted state (I'm using a modified, quick-and-dirty XOR cipher for that. It's secure enough for my purposes and faster than the stronger encryption). Anyhow, what I would like to do is read a block of data, de/encrypt it (in memory) and then write the changed bytes to the same location they previously would have been within the file.
I've found the problem a little outside my programming abilities, so I was wondering if anybody had a pre-made solution, links to appropriate examples, or an all out explanation.
I am writing a program to upload file to the web using Socket and FileStream. Here is the code
Private Sub Read(ByVal state As StateObject) Dim filestream As FileStream = state.fileStream filestream.BeginRead(state.readBuffer, 0, StateObject.readBufferSize, New
In my application, i am downloading file from DMS system to my server. Once the file gets downloaded, on some environment, the iis keeps lock of the file and when the application tries to redownload the file and put the file on same location, an error is generated that file is being used by another process. Following is the code :
I am using iTextSharp with VB.Net to stamp images onto PDF documents. (Since this is not language specific I tagged for C#, too.)I have two applications using the process.The first uses the bytes from the memorystream to display the PDF documents online. This piece is working. The second uses the same function but instead saves the PDF to a file. This piece generates an invalid PDF.
I have seen some similar questions, but they are all creating a document initially and have a document object in the code. Their memory streams are corrupt from the outset. My code does not have a document object and my original memory stream opens fine.
Here is the place where I get the error: (I have to put the buffer from m into a new memory stream because the stamper in the fillPDF function defaults to closing the stream unless marked otherwise.)
Dim m As MemoryStream = PDFHelper.fillPDF(filename, Nothing, markers, "") Dim m2 As New MemoryStream(m.GetBuffer, 0, m.GetBuffer.Length) Dim f As FileStream = New FileStream("C: emp.pdf", FileMode.Create)
I'm trying to remove the first and last lines from a text file. Obviously the last line will be at an undetermined position (i.e. line 50 or 5000). I couldn't figure how to remove the lines, so I wrote code that would rewrite every other line:
I'm working on something whereby I write and read alot of data to disk directly as bytes. But I can't figure out a foolproof way of delineating data structures chained in a single file. A null byte obviously wouldn't cut it, because that could occur within the data structures themselves. Theoretically, any pattern of bytes can potentially occur within a data structure. Does anyone have any ideas for a byte pattern that I could use as a flag for my streamreader? Anything reasonably short, since it's going to be pretty complex, streaming through each file twice, once byte by byte to find the flags and again to split the stream.
Dim fs As New FileStream("C:est.txt", FileMode.OpenOrCreate, FileAccess.ReadWrite)Dim b As New StreamWriter(fs)
b.WriteLine("hellothere") : b.Close()
b.close is necessary to save changes to the file, but then, fs will be closed, too. is there any method that does the same thing but doesn't close fs, like "b.save"???
VB 2005 now offers different methods to write/read a file, such as the File.WriteAllText, the My.Computer.FileSystem.WriteAllText and the StreamWriter.Can anybody explain when is it better to use which method, which one is more efficient in term of memory/processor use and performance time?
I need to download a bunch of pages from a web server, ie. spidering. I know that servers are typically configured to only allow a couple of concurrent connections from a given IP, but that would already halve the total time to run the script instead of downloading one page at a time.
encountering a problem when trying to write data to a text file. If I put the output into a messagebox I can see it, but when I attempt to write it to a file it is just blank. What am I missing here? EDIT - This is just a simple winform that I specify a path to a local HTML file in Textbox1 and I'm attempting to parse some HREF tag data.
Imports System.IO Imports System.Text.RegularExpressions Public Class Form1
I need to add a row of data to an exisitng TextFile that is in Tba delimited format. My program currently used ADO to read and update the table but that was creating to many problems with varying 3rd party providers of the Text File.
I am using the following code to write and empty (dummy) file to take up the remaining space on a device.RemSpace is a Public Variable declared as Long I have a function that gets the remaining space on the device and stores in the RemSpace variable (in bytes). I have tested with a msgbox to display the result of RemSpace, and it comes back correct (not 0). However, when the following code attempts to create the dummy file, the file is properly created but is only 0 bytes. What am I missing here?
I have a code which reads a text file through streamreader,selects what is important and writes the same to another fileusing streamwriter. The problem is that the streamwriter stops writing beyond a certain line and just doesnt write ahead.What can be the problem? Do I have to make two seperate files?
In the following, Response.Write poduces the expected result of displaying user name and password - but nthing is written to the text file (colocated in the root directory).[code]...
In the following, Response.Write poduces the expected result of displaying user name and password - but nthing is written to the text file (colocated in the root directory).
Imports System Imports System.IO Partial Class getCustomer
