Random Access File Format?
Jan 15, 2010
I am moving all of the prgrams that I have written, to VS2008. However, I use Random Access File Foemat for the databases that have been used for over a decade. I need to be able to read and write to a Random access file.I have multiple fields in the database and cannot lose access to this information.VS2008 doesn't use the following type of code to define the Fields that will be used in the Database. I did what it suggested, using the Structure / End Structure, but that was as close to a solution that I could find in the Help Files.
Type EquipType
EquipName As String * 32
Location As String * 28[code].......
View 2 Replies
ADVERTISEMENT
Jan 7, 2009
I am writing a program to calculate Pi to several hundred billion decimal places and this will require lots of GB of memory. I wrote a test program in VB2008 that saved the first 16 digits of Pi (without the decimal point) to both a text file and a random access file, just to be sure it was outputting the numbers properly. For reference the first 16 digits of Pi are:
View 8 Replies
Oct 19, 2011
Years ago when coding with VB6 and earlier, I used a file open command to create, read, and write a file that made it easy to store useful information.I believe it was binary and you wrote/read the data to a specific line in the file. When you opened the file with something like notepad, it just showed random ascii chars. When I needed a line of data, I could specify what line to load it from.
View 2 Replies
Jul 1, 2010
I need an example of how to create and use a random access file
View 3 Replies
May 20, 2010
Created Structure
opened file using FileOpen(1, "filename.dat", OpenMode.Random, , , bytes in structure)
used structure .ID = record number
FilePut(1, structure)
FileClose(1)
The program enters the first record but although when I enter more records it still shows only one record in the file.
View 2 Replies
Jun 23, 2011
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
FileNum = FreeFile()
[Code].....
View 3 Replies
Apr 25, 2010
I'm doing a Program for a Friend of mine, He Want to have a Console Program Running on his Computer.OK the problem i am having is With Stream Read, I have 3 test users inside Test File, if User 1 logs in his information is store in logged file with time and data.but if User 3 logs on user 1 2 and 3 are all saved on the logged file
i dont have read to end of file in my Code.i dont have my Program with me, so i going off the top of my head i have something like this what i want to be able to find out how to do is Right from any part of the file and out put it, I take it i need to use Random Access but how to i code Random Access for this type of file. All i can find is how to Randomly place Words in a text file with Length and size.
[Code]...
View 16 Replies
Mar 2, 2010
I achieved reading and writing data to a random access file, buthow do I write and read data from a certain position in the *.txtfile? Would it be better if I created multiple file modes to
View 2 Replies
Jan 30, 2010
I am using Visual Basic 2009 to create a file of records to store students tests scores.Currently i can write to the file, create new records etc. However i cannot edit a particular record, im sure i have to use file seek function but i have no idea where to start.here is some of my source code to give you an idea of where im at
Do While (Not EOF(1)) And found = False 'loop until no more records or the record is found
nosrecords = nosrecords + 1
FileGet(1, onestudent, nosrecords)[code].....
View 3 Replies
Nov 2, 2009
how to read and write random access records in .NET. Now I know random access files are dead and the response on every query I found with google/bing/yahoo searches was don't use random access use Binary serialization but I can not. I have a situation where I need to read and modify 256 byte records in a file that is used by another application.
Now for a bit of background the file is made up of 27 fixed length records of 256 bytes. Each of the records has a separate structure consisting of 30-120 fields. The proplem I am having is I can create the record structures but when using the FileGet method I am receiving an error. Now I have found samples that showed the same format I am using that claim to work.
The error I am getting is Option Strict On disallows narrowing from type 'System.ValueType' to type 'ProgramName.ModuleName.Record' in copying the value of 'ByRef' paramater 'Value' back to the matching argument.
The basic layout (simplified) is as follows:
Code:
Structure Record
<VBFixedString(6)> Public SomeParam as String
Public SomeNumber as Short
[Code]....
Now the overloads for FileGet show all of the data types including Object. But I have tried various methods to retreive the 256 byte record but without success. Do I have to actually read each of the several hundred fields of the structure one by one? Or am i overlooking something (I have been known for this in the past)
Or (and I'll kick myself if this is the only way) do I just have to set option strict Off in the module and the code as above will actually work.
I would love to be able to just ditch the random access file but I have to keep it for compatibility with several other applications at this time.
View 14 Replies
Sep 3, 2010
The application reads information similar to a DXF file. For purposes of discussion, the data consists of lines, those lines have endpoints, x1,y1,x2,y2. Within the file those lines create "paths", in other words, they are connected. There can be many separate paths within a single file. However in the original file, the geometry is not in any particular order, the paths are not indicated.
View 3 Replies
Nov 17, 2010
I'm tasked with the job of creating a javascript version of a units conversion application written in vb6. I have the source code but I don't have vb 6. The source code uses a dat file to hold a conversion array (unit type, unit, xfactor, plusfactor). Getting the data out of this file would be good to me. I tried creating a little app in vb 2010 to write the data from that dat file to a txt file using essentially the same code as the source code. And that has been somewhat successful (took a while to figure out the fixed string business). Now I can pull the data out as an array. The math elements of this array look fine but the strings are somewhat read-able but too garbled to use. I can't seem to fix that by changing the character set/encoding.
View 3 Replies
Feb 24, 2010
This time, basically, i'm working with Random Access Files.I have this et of code to read data from a form a save it into a .dat file. This works fine.
Public Class frmDramaClub
Structure MemberRecord
Dim ID As Integer[code].....
View 5 Replies
Jan 12, 2010
how to proceed. One of our customers is going to be sending me a flat file (ASCII-Text) that I have to break down and scan. Every line ends in a CrLf - So I know I can use StreamReader and ReadLine(). I did get it to work on one of the test files they sent.(A very Short file) However, the file is not delimited at all and every field is padded to the full length they specified. Here's the format of the file:
[Code]....
View 7 Replies
Dec 24, 2011
I have a flat file that is sorted by account number. I am migrating an application that was in vb6 to .Net. The application uses Random file access and uses a binary sort method to find a record.
Here is the code
Do While (low < high Or low = high) And (f = 0) 'Checking for an account match
middle = (low + high) / 2
FileGet(FileNum, Record, middle)
If Account < Trim(Mid(Record.Data, Byte1Start, Byte1Len)) Then
[Code] .....
From reading up on this in .Net it seems that using the Binary Reader seek method would be the alternative to using old vb6 random access code. The problem is the Binary Reader Seek method goes by Byte position instead of record number. How to convert my code to use a binary reader.
View 2 Replies
Jul 14, 2011
When you need to do random access to the lines of a text file, the regular solution is to put those lines in a list and access them in that list.But doing this if the text file is large creates a large memory overhead and may cause some memory stress on the application.This class maps the file and provide the ability to read any particular line in the file at a random position, without the need to read or put in memory any other line but the desired line. The only memory overhead involve is the 1024 bytes buffer of the base stream.Even if the file mapping can be a process that consume a noticable amount of time if the file is very large ( ~ 5 seconds for each 100,000,000 caracteres) , once the mapping is done the access to a particular line becomes instantaneous regardless of the size of the file. (The file mapping can always be done at a convenient time (ex when the process load) and can be done on a worker thread The class is base on a StreamReader to support the differents Text Encodings Example uf usage ( As I say, if the file is very large, dont do it like that, but declare the class at a convenient time)
Imports Reader = System.IO.MyStreams
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
[code]....
View 11 Replies
Jun 27, 2012
i Have Used Database file for storing Data in my Application.Now I want to take backup of data in Access, Excel or in Any other Format.
View 1 Replies
Oct 29, 2010
This is probably a pretty novice design question. I'm trying to work my way through a number of requirements and give the users the experience they're looking for.I've written a tool that does big calcluation-type things. It currently consists of a class library and command line tool (separate .NET projects.) We're using an Access database format as the file type because it can keep all the various tables together in one file. A few other items about the application: There are not many users. There are no concerns with scalability. There are not great concerns with updates. Desktop is desired. Not web.Using VB and .NET 3.5 SP1
I now need to develop a GUI front end that will allow typical File/Open and File/Save type operations.Users expect that they can open a file, edit it some, then either choose to save it or close it unsaved without any changes being written back to the file. Saving it would obviously save all changes affecting all tables back to the file.
Does it then make sense to use a temp file for something like a proxy then? To, when a user "opens" a file, copy the source Access file to a local temp file and then use that for the editing session? Then, if the user "saves", copy the local temp file back to the source path?
Update: [tagged with ms-access tag too] Also, I omitted the fact that users would expect typical File / Save As functionality too. I think the design I've put in question in this post is what is traditionally called the Proxy design pattern. Has anyone tried this (successfully!) with Access database files before? Words of caution or advice?
View 2 Replies
Feb 25, 2011
I'm trying to use a GUID to generate 6 random alphanumeric characters (just letters and number). Is there a way to change the format of a GUID before it is generated. Or must I generate the GUID in its standard format and then manipulate it.
View 5 Replies
Aug 9, 2009
my form is connection to an access db ....called Quiz.db , it has 10,000 questions and answers , i want to click button and generate random question with correct answer , so ID# of record must be random on load and click next?
View 3 Replies
Jul 27, 2011
I am trying to convert a VB5 program to VB2010 so that I can continue to support it on my new PC. My copy of VB5 was an upgrade from VB3 which was an upgrade from VB2 which came on floppies, so I can't just install every preceding version as my new PC doesn't have a floppy drive.I have accepted that I will have to design all the forms from scratch (whatever happened to twips?) and will have to go through the thousands of lines of code line-by-line, but I have hit a brick wall when it comes to random access files. One such file is defined in the Declarations section of Module1 thus:[code]....
I soon found I had to change Type to Structure, but then in the declaration of transrec, transtype acquired a wavy blue underline with the error message: "'transrec' cannot expose type 'transtype' in namespace 'Treasurer_2010' through module 'Module1'.So if I can't use the structure in the module in which it is declared, where can I use it?
View 4 Replies
Oct 30, 2010
I have 15 years' worth of files (approx. 10,000) that were created using VB6 structures and stored using the random access method. I am trying to write a conversion routine that will read the old structures and put them into a new format that is more compatible with the .net environment. I have not been able to successfully read any of the old files using the tools available in .net. Each file starts with a header record structure. The header record tells me how many tags are in the file. The next record (ie record number 2) is the first tag pointer record in the file.
There are num_of_tags of the pointer records. Each pointer record has the string that holds the tag's 'literal name and two long integers that tell where in the file this tags records are. Those actual records are stored as History data structures, [Code]
View 10 Replies
Sep 6, 2010
how do you save data stored in an array of records (structure) to a text file using StreamWriter? I currently have
Private Sub btnSaveToFile_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSaveToFile.Click
Dim sw As New StreamWriter(New FileStream("EmployeeDetails.txt", FileMode.Create, FileAccess.Write))
For Each record As EmployeeType In employees
[code]....
but it doesn't work. My array is fixed and currently has 3 elements (for testing purposes). If I enter two records and add these to the structure I get the following data saved to the text file:
123,helen,66000
879,john,89975
0,,0
How do I stop unused elements of the array being included when writing to file? Should I use a dynamic array instead and if yes, how do you use dynamic arrays with structures?
View 1 Replies
Jan 16, 2012
I'm trying to convert an old Quick BASIC program to VB.Net. There doesn't appear to be any direct replacement for the old file statements. Building a database seems like overkill for my simple needs.
How can I do the following in VB.Net?
OPEN "test.dat" FOR RANDOM AS #1 LEN = 20
FIELD #1, 10 AS a$, 10 AS b$
LSET a$ = "One"
LSET b$ = "Two"
PUT #1, 1
GET #1, 1
PRINT a$, b$
CLOSE #1
View 1 Replies
Jun 22, 2010
I am trying to generate random images from access database using hashset as it is said to be unique and there won't be any repeated images appearing. But, it doesn't seem to work.
How can i get it to work? By the way, i am very new to the concept of hashset.
Private Function GetImageFromByteArray(ByVal picData As Byte()) As Image
If picData Is Nothing Then
Return Nothing
End If
' is this is an embedded object?
Dim bmData As Integer = If((picData(0) = 21 AndAlso picData(1) = 28), 78, 0)
' load the picture
Dim img As Image = Nothing
Try
Dim ms As New MemoryStream(picData, bmData, picData.Length - bmData)
img = Image.FromStream(ms)
Catch
End Try
' return what we got
Return img
End Function
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Panel1.Visible = False
Panel2.Hide()
Dim conn As New OleDbConnection
Dim DA As OleDbDataAdapter
Dim DS As New DataSet
conn.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=db1.mdb;User Id=admin;Password=;"
DA = New OleDbDataAdapter("Select Empty, EmptyName, Target, TargetName from PicturesDisplayed", conn)
DA.Fill(DS)
Me.PictureBox1.SizeMode = PictureBoxSizeMode.StretchImage
Dim oledbconnection As OleDbConnection
oledbconnection = New System.Data.OleDb.OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:Documents and SettingsAdministratorDesktopdb1.mdb;Jet OLEDB:System Database=system.mdw;")
oledbconnection.Open()
Dim command As OleDbCommand
command = New OleDbCommand("select count (*) from PicturesDisplayed", oledbconnection)
Dim count As Integer
count = command.ExecuteScalar()
oledbconnection.Close()
Dim randomImage As New HashSet(Of Integer)
' Create a integer and new Random object
Dim intPic As Integer
Dim rand As New Random
'Pick a random number between 0 and the number of images in database
intPic = rand.Next(0, count)
randomImage.Add(intPic)
PictureBox1.Height = 256
PictureBox1.Width = 256
PictureBox2.Height = 256
PictureBox2.Width = 256
Dim pic1x As Integer = _
(Me.ClientSize.Width - PictureBox1.Width) 2
Dim pic1y As Integer = _
(Me.ClientSize.Height - PictureBox1.Height) 2
PictureBox1.Location = New Point(pic1x, pic1y)
Dim pic2x As Integer = _
(Me.ClientSize.Width - PictureBox2.Width) 2
Dim pic2y As Integer = _
(Me.ClientSize.Height - PictureBox2.Height) 2
PictureBox2.Location = New Point(pic2x, pic2y)
' Now set the picturebox image equal to the image chosen from the array randomly using the random
PictureBox1.Image = GetImageFromByteArray(DS.Tables(0).Rows.Item(intPic).Item(0))
PictureBox1.Visible = True
PictureBox2.Image = GetImageFromByteArray(DS.Tables(0).Rows.Item(intPic).Item(2))
PictureBox2.Visible = False
If (randomImage.Count = count) Then
Me.Close()
End If
End Sub
View 1 Replies
Nov 30, 2010
how can we or can we import data from PC RAM, and stored it to data like text or grafik...
View 6 Replies
Dec 12, 2010
I'm am trying to determine the total number of fields under a particular heading given that the other Heading's total number of fields are > or < than the heading in question. The query, shown first in the attached code, works well if there is one column in one database table, however it does not work well when there are a number of columns with a different number of fields respectively. The CategoriesID encompasses the entire tables contents.I devised a function to determine the total number of fields within a particular column and then attempted to incorporate this, without success, into the second query, shown in the code.
Private Sub GetRandomHeadingFields()
Dim varNumberHigh As Integer
varNumberHigh = TotalNumberofHeadingFields()
[code]....
View 2 Replies
Jan 24, 2009
I'm working with random access files. I created a module and in it put the
Structure PersonData
Dim Name as String
Dim Age as Integer[code]....
The problem is strange... it will let me input string lengths of 3 for Person.Name and Person.Description and it will save correctly, however, the moment I try and lengthen the string (or even if it's longer than 3 to begin with), I get a 'bad record number' error.
View 2 Replies
Mar 3, 2012
how can I retrieve random data(questions) from access 2007 using vb 2008?
View 4 Replies
Apr 19, 2011
I have recently decided to give .net another chance, but i have a few questions about it before i get really into it. RE: Files, I use random access files to store data as opposed to databases (namely i don't see the need for a database for storing so little information(records <200 max) knowing that it is an older system and less "cool" i don't care...) Will vs2010 express read, write to random access files? Would it be done kind of like vb6 (which is my current vb version)? I will be needing to print the text of rich text boxes, is vs2010 express capable of doing this?
View 7 Replies
