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]....
Below is the part code I currently use to write to a file,
Try
Using sWriter As New IO.StreamWriter("C:Tmp.txt", False)
sWriter.Write(m_Buffer.ToString) : sWriter.Flush()
End Using
Return True
Catch ex As IOException
End Try
But some time this results in error
Access to the path 'C:Tmp.txt' is denied
My question is, Is there a safe way of detecting File access permissions, without handling exceptions, I mean if I can some how check before opening a file for any filehandle opened for it.
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.
I'm trying to update the UI from a background thread, but the method I'm using at the moment isn't working. From what I've been reading, the method I'm using should work, but it isn't.[code]...
View 8 Repliesam programming a media player in VB.Net using the Microsoft.DirectX.AudioVideoPlayback namespace. I would like to be able to play video files which have multiple audio streams (eg. several languages or commentary) and select which audio stream to play. As far as I can tell the Video and Audio classes don't provide this functionality.
View 1 RepliesHow can I point or target my access database in a safe way?
View 3 RepliesI am trying to write a thread safe application that contains 3 threads : -
1 - Data acquisition and decoding
2- Data graphing
3 - FFT and filtering
Thread 1 is collecting bytes from the serial port and converting them int integers (so taking two bytes) after is has captured 64 Bytes and converted into 32 integers, it then needs to pass the array to the graphing thread.
The graphing thread then plots the data and waits for more data.
Thread 3 also waits until thread one has collected 2023 integers and takes these and performs some FFT calculations (which take time).
My question is how do i share the arrays between the three threads without deadlocking the program? as the serial thread will be flying around reasonable fast (1000 bytes per second) so it will synclock onto the shared buffers for most of the time.
Originally i was going to use two synchronised queues, so when thread 1 has collected 32 bytes it queues the data into the graph queue, and once it has collected 2023 it queues the data into the FFT queue.
Then thread 2 and 3 can simple dequeue the data.
However using queues has the overhead of casting the data in and out, and as i know the data type i was planning on using two arrays :-
Dim GraphArray() as ushort
Dim FFTArray() as ushort
Then Thread 1 adds data to each thread, and thread 2 and 3 simple wait until the correct amount of data is available before removing the data. my question is there an array type that allows me to remove x amount of data from an array?
Because i cannot do this easily with the ararys defined as above (GraphArray, FFTArray), as i was planning on making them 1mByte and allowing thread 1 to fill them Knowing they should never overflow and then let thread 2 and 3 remove x amout of bytes at a time unless there is a better way of doing it
How do you access a link with rel="alternate" using process.start?
Dim Internet As New Process
Dim InternetAddress As String = eL(DiUs, 0)
Internet.StartInfo.FileName = InternetAddress
Internet.StartInfo.WindowStyle = ProcessWindowStyle.Normal
Internet.Start()
eL(DiUs, 0) is a link to an RSS, but the post won't show unless the link is rel="alternate". How do I do that?
<link rel="alternate" href="http:..........." type="text/html" />
Whether using XML database for data storage is safe enough? because I wanted to branch using an XML database and then she sends the data to the center. and then the data is in process at the center and then incorporated into the database server
View 4 Repliestrying to find a decent answer for my question; I do have a utf8 file which I (down)load, manipulate and wanting to save back again.The result always is that the file I produce is not in utf8 format;
Dim fs2 As New FileStream("c: est.dat", FileMode.Create, FileAccess.Write, FileShare.None)
Dim w As New BinaryWriter(fs2, Encoding.UTF8)
[code].....
My application runs on a "server" machine and provides files (10megs - 100megs each) to 8 other computers. Currently this is done using a standard shared folder on all 8 computers and the server simply copies the file to \ComputerNameSharedFolder - and everything is great.However, due to new policies we need to remove all shared folders, so using a simple \ComputerNameSharedFolder is no longer feasible. Therefore I need to find a way for my application to be able to share these files in a safe, secure, and compliant way.There has been talk of using sFTP which would require each system to have an sFTP server running at all times (controlled by the application somehow), or also SSL was talked about as it can be integrated into the application easily, etc...
View 1 RepliesWell im making a program that will Add the Safe File Name of the File opened in the Open File Dialog to the first column of the listview and the File name and path to the second. What i want it so when i double click on the Safe file name it will open the file specified in the path in the second column.i already got the add file to it.
View 4 RepliesTaking up 3gbC:Documents and SettingsAll UsersApplication DataMicrosoft Visual Studio10.0TraceDebugging.
View 3 RepliesIs it safe to use something like this to ensure that a directory isn't currently being written to? [code]I'm processing images which can be up to 10MB so my main concern is that I'm not sure whether the LastWriteTime property (which presumably references the filesystem 'last modified' meta data) is updated when the first, last or every byte of a file is written to disk.Files will generally be uploaded via IIS7 FTP to an NTFS Filesystem on a Windows 2008 server. If it's filesystem-dependant though it would be good to also know which filsystems update when. I'd hoped that this could be used to simplify the programme by ensuring that the whole directory was processed at once. In the end I decided to rethink that since the workarounds are messier and less reliable than the one I was trying to avoid!
View 3 RepliesI have searched far and wide and have not been able to find a solution to my problem.I have a typical situation where a process is gradually eating up memory. The process eventually throws an OutofMemory Exception. This problem has been dealt with in the past by just building a special machine that has greater memory.
This process bombs on only one of our clients which has around 450,000 records. We iterate through the collection of accounts and build a class object that is then passed into the xml serializer. This object has several properties and methods that would not all be populated at the same time. These objects are populated based on the information in each account record.
I've checked on the way we call the contructor for the XML Serializer and it is in the format that would store the xml assembly and not create new ones each time. So, I do not believe there is a memory leak due to the creation of the dynamic assemblies.How we call the serializer: Dim k1Serializer As New XmlSerializer(GetType(ClassObject))
My questions are:When serializing a large object, does the serializer look at every possible serializable object or just the ones that are populated by your object?
Could the serialization of this large class object be causing an issue?I noticed when we pass in the serialized object, it's not automatically written out to the file specified. It takes a few seconds to, I guess, serialize the object and then write it out. Could the fact that we are iterating over so many records, so quickly, that the serializer is not having enough time to write out to the file and then release the memory?
I am experiencing a strange issue with a VB6 -> VB.Net conversion. There is a function that uses ADOX to look through the tables in a given database, and reset the seed values of any columns in said tables with the auto increment property set to true.I tracked the issue down to a call of "col.Properties("Autoincrement").Value". If this line of code is commented out, then the file handle properly terminates when I close both the ADO and the ADOX connections at the end of the function. If I leave that line in, the handle stays open despite the closing calls and forcing garbage collection.Here's how I am closing the objects:
System.Runtime.InteropServices.Marshal.ReleaseComObject(adoConn)
Dim connection As ADODB.Connection = cat.ActiveConnection
If Not connection Is Nothing Then
[code]....
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.
I want to create small database which handles Student Attendance Record it will store the roll calls of students on daily basis that teachers collect from the students in the class on paper and then later transfer it on computer .So my database Must contain Month, Year, Program (BCS, BIT, MS, MCS, MIT etc) Batch (1st, 2nd etc) and Subject (English, Math, Geography etc)
Suppose I want to Search for the Attendance Sheet of any month, year, Program, Batch or Subject, it returns me the required dataSo i come up with the Datadase which includes 5 dimension tables and one fact tableDimension Tables1. Student (StudentID, Name, other Attributes)2. Program (Program_Name, other Attributes)3. Date (Date, Week, Month, Year)4. Batch (Batch_Number, Description)5. Subject (Subject_Name, other Attributes)Fact TableAttendanceTable ( StudentID, Program, Date, Batch, Subject, Status)but the problem come when certain columns are repeating again and again which is time consuming for database operator and shows inconsistent behaviour of database.
Look at it: my Fact table would be like this [code]....
problems:1. The StudentId is repeating which shouldn't (Primary Key),2.It wastes a lot of time coz i'm repeating the data again and again Like Program, Date and Batch which shouldn't be in consistent Databases.
I have this code for compressing datasets into files:
Using fs As New System.IO.FileStream(flnm, IO.FileMode.OpenOrCreate, IO.FileAccess.Write, IO.FileShare.Write)
Using zStrm As New System.IO.Compression.GZipStream(fs,
[code].....
I am serializing and deserializing a class - and sending it around with httplisteners - code looks like this Dim inputstream As Stream = request.InputStream()Deserialize(FSOb, inputstream)With the Deserialize function looking like this (and the Serialize as well - it deals with a memorystream)
Public Sub Deserialize(ByRef FSOb As FSObject, ByRef st As Stream)
Dim bf As New BinaryFormatter()
FSOb = CType(bf.Deserialize(st), FSObject)
End Sub
[Code]...
I found that the overlay function was working fine. However, it seems that if I use the overlay function while reading an image from a stream, that it would enlarge the picture before overlaying it.
ie:
overlay = New Bitmap(stream)
g.DrawImage(overlay, 0, 0)
Seems to enlarge the image before overlaying it, whereas this:
overlay = New Bitmap(My.Resources.Pic)
g.DrawImage(overlay, 0, 0)
Seems to overlay the image fine.
What could be the reason for this?
I am new to .NET from VB6. So I do not have any background with streams, however the concept seems straight forward. I am trying to populate a listbox using the ADD method with the data originating in a text file. Using a stream reader I am aquiring the data (I can prove that the data is there at every itteration using the debugging tools). However, it doesn't make it into the listbox. I have other data appear withn the listbox in a couple of different ways just to prove that there is nothing wrong with the way the listbox is setup or coded. The listbox is a single instance item on a form, all setup is done through the properties window.
[Code]....
I experimenting with the Twitter streaming api, an am trying to open a stream for a user to consume events as they happen. I using a standard set of classes for making REST api calls to twitter. When using url... in a "GET" call the response stream never ends.I'm opening a StreamReader and reading the response as I would with any other REST call to Twitter. This is probably obvious to others, but how do I "consume" this stream... Is there a way to read the StreamReader as it's reading (meaning before it closes)? or maybe there a different method I can user to consume this stream.... again, I apologize if this seams to be elementary to some, but I can't figure it out at the moment. Here is the original source I started troubleshooting this with.This method was fabricated from a set of C# Classes I found in a forum on LinkedIn. At the line that reads "responseData = responseReader.ReadToEnd()" the method starts to "drink" the stream... but do so like a bottomless cup... reading this stream of data in real time before it closes (which is essentially until I stop debugging or kill the process) is the question I'm tackling.[code]
This write the opened twitter stream to the file, and every time I Tweet, Retweet, Delete, Direct Message... and so on.The file grows with a JSON object appended to the text. I used the Do While 0 < 1 for testing here, because I just wanted to see it working. I see on MSDN StreamReader Constructor Description that the New constructor is supposed to accept a Boolean value for "leaveOpen", but no such argument allowed when I try to add this to the constructor.Does anyone have a good example of how to do this with forcing and infinite loop or just a better approach than this... I would like to simply read new updates sent each time from Twitter, and address them accordingly? There is obviously a way, I'm just new to the concept of consuming a stream like this with out it being closed.
I want to be able to take snapshots of the desktop periodically(about 1 every 300 ms) then be able to view them live through a web browser.
Here is what I already have:
I already have a form which takes the snapshots, overwrites a file called 1.jpg with the image. I also already have an http server running which succesfully serves up html documents.[code]...
I build an application that has two forms; one gets an employee info and stores in on a txt file (I accomplished that) and the other for viewing the records and searching for a record. I'm having troubles with viewing the records one by one when I click on the "Next Record" button.
The code below is only for view form
vb.net
Imports System.IO
Public Class frmView
'Dim strFilename As String
[Code] .....
i want to add data into my MS access file with VB9.. i have got :
1) BatchNumber
2)Barcode
3)CodeNo
4)Expiry Date
all the things which i need to add are in textboxes except for "CodeNo" which is in combobox.
Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click
Dim con As OleDbConnection = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:Documents and SettingsuserDesktopBaxterBaxterOCR_new.mdb;Persist Security Info=False;")
[code]....
Anyone tell me how to save data to ms access file
View 1 RepliesI'm using Microsoft.Jet.OLEDB.4.0 to set/get data from database access file, but it isn't working perfectly on 64-bit systems, so I'm looking for an alternative way.set/get data from database access file working on 64-bit systems.
View 1 Repliesi have a simple vb program which i have loaded a data surce access file with it. I have done this using the data scource tab/wizard and then dragged the table on to my form which automatically gives me the functions i need (e.g. next record, save record, add new etc..)This all works as expected and fine within the program but when I open up the access file after - it hasnt done anything to the database/table what so ever - i.e. no changes were applied to it. Im so baffled
View 4 RepliesI have a pdf file which I need to extract information from. the pdf has a table and I need to get the information of the last column. is this possible in vb.net?
View 2 Replies