Editing Record In Random Access File?
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].....
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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.
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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:
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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.
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Jun 21, 2010
I am having problems editting my record where i basically want to select a record from the datagrid view and change any details where the data is displayed in the text boxes i have put on my form and click edit and have the data updated on to the database as well as the dataset. As for my updating button the code seems ok but i check my database and it doesnt change. Here is my code where the edit and update button code are at the bottom:
Imports System.Data.OleDb
Public Class Stock_Control
Dim dbConnection As OleDbConnection
[CODE].....................
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Jul 1, 2010
I need an example of how to create and use a random access file
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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.
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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].......
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Jun 23, 2011
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
FileNum = FreeFile()
[Code].....
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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]...
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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
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May 30, 2011
in my visual basic 2008 express edition project I have 2 forms (paxreportfrm,paxsearchfrm).I want to give inputs in paxreportfrm and save the record(which is working fine).then in paxsearchfrm i want to search depending on multiple criteria (working ok).when i click on the record which is in gridview in the search form,opens up the paxreportfrm again with all the details of that specific record (working fine). Now i want to update the existing record which has been populated from the gridviw of the paxsearchfrm and also want to have the option to delete the record.I am using the datacontrols(wizard) to make connection with the access2007 database.can someone give me some example of how to do the Edit and delete in the database pls.I already have a save button on the paxreportfrm(if i click on that, after changing the details on existing record, it just saves IT as a new record).so i really need something which will actually save the modifications on the existing record AND ALSO WILL BE ABLE TO DELETE IT FROM THE database. I have tried couple of methods but none of them are working.
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Mar 12, 2011
I have a DataGridView bound to a datatable which comes from an SQL Server database.When the user edits a record my update statement changes the field datetimemodified to reflect the last date and time the record was edited (as stored procedure). The new value for datetimemodified is not brought into my DataGridView.
1) How do I refresh a DataGridView bound to a DataTable? Is there any way to refresh or resync only records that have changed instead of the entire DataTable? (Note: my update statement is working fine. I'm only wondering about refreshing the DataGridView.)
2) Would it be better to change the value of DateTimeModified on the client side so that I can avoid a refresh (assuming that this is the only reason I need to refresh the data)?
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Feb 27, 2009
I have problem, when i click on save it gives me an error.'Cannot perform '=' operation on System.Int64 and System.String.'My code looks as follow....
vb.net
Private Sub ItemsBindingNavigatorSaveItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ItemsBindingNavigatorSaveItem.Click
[code].....
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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.
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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.
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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.
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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].....
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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]....
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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]....
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Aug 29, 2011
Current S/W Access 2010 and Windows 7 (all up to date) also using VS2008 When I was using Access 2003 & 2007 the following VB.Net code line worked fine:
dbs.Execute("SELECT * INTO TrialBOYTbl FROM [Text;FMT=CSVDelimited;HDR=Yes;DATABASE=" & myPath & ";].[TrialBOYDtl#csv];")
But when I use Access 2010 the first data record is missing in every file that I upload - there are no other errors.The SCHEMA.INI file is:
[TrialBOYDtl.csv]
ColNameHeader = True
Format=CSVDelimited
MaxScanRows = 25
[code]...
NOTE: This code line is executed in VB.Net (Interop) in conjunction with Access Automation. Therefore, I believe that I must use DAO
as that is how MS Access is based.My guess is "[Text;FMT=CSVDelimited;HDR=Yes;DATABASE=" looks like an ADO (not DAO???) Extended Properties specification which worked fine until Access 2010.
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Apr 15, 2012
I have a access database with these columns. USER_ID,COUNT,TIMES
Let say the current record is this:
USER_ID,COUNT,TIMES
STEVE20,24,1.5
Now I want to updated the current count record and times, but before updating I want the old record to be added to the new record. What should be my query?
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Dec 7, 2011
I have a BindingNavigator and a datasource, and I want the Next Item button to display in the corresponding textboxes a random record (which was not before displayed). How might I do that?
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Jun 3, 2009
As in today i click on the button it will display the item when i hit again the button it will still display the same item and last for the whole. On the second day, i hit the button again it will display other items and last for thewhole day again.
[Code]...
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Dec 6, 2011
I want to select a random record from a data source (based on an MS Access file), and place the record cell contents into certain textboxes. After the record is chosen, it cannot be selected again.
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Oct 15, 2011
window is loaded, binded textboxes get filled, user edits textboxes and clicks a save button it works, all except crashing with a "vb.net 2010 Concurrency violation: the UpdateCommand affected 0 of the expected 1 records." most of the time but the data does get updated'form.vb code for button_click?
Dim dtNewRow As DataRow
dtNewRow = dbDataSet.Table.NewRow()
dtNewRow.Item(dbDataSet.Table.Column) = Textbox.Text '<--this line is followed by 33 more that vary on column and textbox
[code].....
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Aug 10, 2010
I am making a application that has the ability to edit values on a access database table. As a simple example, My table looks something like this:
Order Number Completed
2000 No
2001 No
2002 No
The application needs to edit the Completed columns. I have 1 text box, and 1 button in my form. You enter the Oder Number in the textbox and press the button. The VB application then needs to change the Completed to Yes in the database. Example, I type in 2002 in the textbox and press a button. The application changes Completed to Yes for this order number in the access database and saves/updates the database.
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Feb 15, 2010
i have used this code to insert information into microsoft access database.however i dont know how to edit information from vb.the coding is below:
Private
Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
[code].....
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May 5, 2010
Im wondering how would i work with a text file. which would allow me to Read the next Record, Cut record out of the program.
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Feb 9, 2011
Basically, I am making a booking system. On one of the forms, you can: Add, Edit and Delete a record by using the selected index. I can do the Add and Edit part fine but some problems are occuring when I try to delete it. What I'm trying to do when deleting is, copy all the records except the selected one and then copy it back into the original file again.
[Code]...
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