FileStream Delineator - Delineating Data Structures Chained In A Single File
Jul 31, 2009
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.
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Dec 22, 2009
I am trying to get the data from the text file to load into an array of structures and then be displayed in a listbox on FormLoad with no luck, all I get is a blank listbox.
Code:
Public Class frmMemList
'Create a structure to which data from text file MEMBERPHONES.TXT will be read.
Structure MemberList
[code]....
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Dec 22, 2009
I am really struggling lately for some reason. I do not know why, but I can not get simple programming code to work, usually due to simple mistakes. Anyway, enough about that.Here is my code, I am trying to get the data from the text file to load into an array of structures and then be displayed in a listbox on F
Public Class frmMemList
'Create a structure to which data from text file MEMBERPHONES.TXT will be read.
Structure MemberList
[code].....
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Sep 29, 2008
I have written a ActiveX DLL in VB 6 which is like -
[Code]...
When I do this everything works fine and I am able to pass value to dll. I am passing two structures arrays and other single values like int and double etc. So far so good. But when I insert this code in another application (created in same vb.net 2005) where I actually intent it to use then i get the following error -
System.Runtime.InteropServices.SafeArrayTypeMismatchException
Specified array was not of the expected type.
I am puzzled as to why is this happening. I checked basic settings and they are same. In short the code works if i create a new project and go on but does not work and gives error if I insert in an existing application's code where i wanna use. To test I created a dll without passing structure arrays and then it worked in that application.
[Code]...
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Nov 25, 2008
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
[Code]...
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May 13, 2010
I am trying to write the inputs retrieved from a form into a single csv file. The code that I currently have creates a new csv file everyttime I click the upload button. Is there anyway that I can alter my code to save all the data into a single csv file? [code]....
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Oct 30, 2009
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]
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Nov 29, 2011
If you have
[Code]...
The question is when I do task.Wait(4000, cancel.Token) this should ultimately fail as the ContinueWith task won't complete within the timeout. It seems the Wait only applies to the Task and doesn't take the chain into account, how can I have it wait until the "chain" is complete?
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Apr 16, 2009
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....
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Feb 18, 2010
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)
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May 19, 2012
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.
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Jul 27, 2009
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
[Code].....
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Jan 21, 2010
I am currently working on a project for myself which looks through employee's information to find their availability to work. I've tried making a structure which holds the employee's information but I can't think of a good way to create different instances of it and store information in it at runtime. I'd prefer to load the information in at startup and not have to declare each employee and information. I am very new to Visual Basic 2008 but I have a good grasp of arrays from C and C++.
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Sep 1, 2009
Can a list class in vb.net contain Data Structures ?
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Jun 22, 2011
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?
[Code]...
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Aug 7, 2010
I'm wrangling with issues regarding how character equipment and attributes are stored within my game.My characters and equippable items have 22 different total attributes (HP, MP, ATP, DFP). A character has their base-statistics and can equip up to four items at one time.[code]Final character ATP in this case would be 88.I'm looking for a way to implement this in my code. Well, I already have this implemented but it isn't elegant. Right now, I have ClassA that stores these attributes in an array. Then, I have ClassB that takes five ClassA and will add up the values and return the final attribute.However, I need to emphasize that this isn't an elegant solution. There has to be some better way to access and manipulate these attributes, including data structures that I haven't thought of using.I should note that there are some restrictions on these attributes that I need to be put in place.E.g.,these are the baselines.For instance, the character's own HP and MP cannot be more than the baseline and cannot be less than 0, whereas the ATP and MST can be. I also currently cannot enforce these constraints without hacking what I currently have :(
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Feb 10, 2010
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 :
[Code]...
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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).
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Jan 20, 2009
I have a structure called 'Scheme' and in my program I want (ideally) an ArrayList of 'Schemes' (so i can add, remove schemes etc.). However, within the 'Scheme' structure, I want to have an ArrayList of 'Item''Item' is another structure. Are there any solutions out there for iterating through these arrays quite easily?
How can I easily add multiple Items to a Scheme and mutliple Schemes to my Scheme array. Code is below. When I try to add Items to a Scheme, I get the 'Object not set to a reference of an object, try the 'New' keyword', but you cannot declare 'New' keywork within a structure.
[Code]...
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Jun 5, 2012
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)
[code]...
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Jan 20, 2010
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:
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Jul 11, 2011
I have a List Table (lstTable) that is on the same form that I am trying to fill in with information from a public structure (ELEM_DATA). I understand nested with statements will work if it is within the same scope but how can I do this with example 2 below:
Example 1:
With me.lstTable.Items(RECORD)
.SubItems(1).text = ELEM_DATA(RECORD).name
.SubItems(2).text = ELEM_DATA(RECORD).number
end with
[code]....
I didnt know if it is possible or if it would be as simple as changing (.name) to something else.
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Nov 29, 2010
I am trying to copy file from server to the Current Pc useing the following code..[code]
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Dec 27, 2011
I need to create a collection of millions of objects, each object has 3 double and one integer fields.If I remember (after more than 20 years without using C) in C you would allocate enough memory using a struct and an array, and read all the file content in one shot.In VB I created a class with the 4 members, and this constructor:
Sub New(BR As IO.BinaryReader)
X = BR.ReadDouble
Y = BR.ReadDouble
[code]....
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Mar 11, 2010
what the results I need in a Windows Form Application.
Requirement:
(1) I need to create class objects with all various methods and properties, etc.
(2) I will create only one instance of the each class
(3) I need to be able to call the methods and properties of the created class objects (1) from any form I create.
(4) I use the class objects to store data so that separate threads can access them..
Question: how I would code this into a WFA? (I have console application code that works but need to convert it into a GUI).
[Code]....
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Oct 21, 2010
My application uses structures that contain strings and arrays that I want to write to disk. I understand that I can create the fixed length data types in the structures by using "ReDim" and "String$", but my question is: Does VB reallocate the storage for the structure which includes these redimensioned members in-line (which would be necessary in order to write the contents to disk), or does it allocate heap and merely store a pointer in the structure?If only a pointer is provided, is there a straightforward workaround to allow me to create fixed length data types in a structure that could be written to a disk file?Or, Is there an I/O method that will handle the situation by recreating a contiguous buffer containing the structure before writing it to disk?
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May 9, 2012
�On load read data from units.txt into an array of structures;�Allow the user to choose a major and then add units to a study plan.Note your program must not allow the user to add units not in the major and a unit can only be added once to a study plan;�Save student first name & last name, student number, unit codes to a user selected file (e.g. fred.txt); �Allow the user to select a student file to load using a common dialog control ;�Display the units for that student.
The program must have the following features:�It must use a common dialog control for saving data;�The program must have at least one general procedure; �The program must demonstrate the use of an array (array of structures recommended).I've attached a copy of the text file needed to be loaded.
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Dec 10, 2010
I save data entered by user into a structure like this
[Code]...
Q1. How can i save that structure into file using binary read write methods.
Ans. [URL]
Q2. How can i save that structure array into file using binary read write methods.
Ans. link to some other tutorial or resource if u know
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Apr 17, 2012
These are the directions for the assignment.So far I am able to get the file read and printed onto a list box.The book we have for the class does not clearly talk about using the array of structure method with formatting an imported text file.After that I'm pretty much having a bit of trouble with everything else.I know I can figure most of it out but what I'm having a big amount of trouble with is the array of structures that he wants.I know that when I have the file imported that I need to save it temporarily and go through it and at every ":" put it in an array and save that spot and then keep scanning through the file. I know it is going to be a for loop using the index to count through but I'm not sure if how to start it.This is how the text file that he wants sorted out looks.
Ally Gators:Tim Tebow:240:280:250
Ally Gators:Albert Gator:150:175:222
Ally Gators:Joe Cool:195:220:217[code]...........
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Jun 27, 2012
I'd like to give a homework assignment to a person learning VB.NET. I'd like it to use basic inheritance and a variety of data structures including queues, lists, arrays, or stacks in a windows forms application. I was thinking of a pizza-ordering application. This would allow them to utilize some basic inheritance and practice using .NET UI elements.
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