Creating A Database Using Structures And Arrays?
Nov 15, 2011
I want to create a relational database in VB2010 and I am attempting to accomplish this goal by creating a structure of records to be stored in a Random Access File.For each record, I want to organize each fixed-length record so that 4-integer sets of data are stored into a a multi-dimensional array.But when I try to write the code below at the module level, I get an error.
Structure PictureDat
'len= needed for Open
of Random Access File [code].....
Since I want to read/write/save the data in this structure to a Random Access File with a fixed record length size, I need to exactly specify the size of the record...which is, of course, determined by the array's dimensions.If I could accomplish this strategy, then I could search this random access file for a match of search criteria consisting of 4-integers with any of the 4-integer sets of data in each record and thus find, edit, delete and search records...therby retrieve information from my database.
Is my program design inefficient? Is there a better way to handle perhaps hundreds of thousands of records? The IDE keeps telling me that I am using a deprecated method of file I/O when I use FileOpen(), FileGet(),FilePut() and should be using MyFile.I am entirely comfortable with my time-tested method of data storage that ensures the security of disk storage while exposing only one record at a time to the PC's volatile RAM, thereby not allowing all my data exposed to possible memory corruption on a PC left on for hours, which would be the case if I loaded the whole file as a monster- sized string or stream. Also, these older file access methods allows my code to run on PC's with modest amounts of memory.
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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 2, 2010
I read in the Book "Mastering Microsoft Visual Basic 2008" about "User-Defined data types".The example given is creating a Structure as follows.I wanted to check that so I wrote all the code given; I used a TextBox and a Button for this.(I didn't include the "CheckDate" here; that is in the book)
Structure CheckRecord
Dim CheckNumber As Integer
[code]....
The problem is this does work.What I get is "00000". and I found out that the "Checks(4)" Array does hold any value ie: on keeping the cursor over that, it shows "CheckAmount 0.0, CheckNumber 0 , CheckPaidTo Nothing ".
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May 24, 2009
I'm currently doing this project where i have to create a program that let's the administrator manage students (and their tests.) I have decided to use Random Access file in this project.because structures will need fixed lengths...i don't know how will i search through the students (a function of the program) when each student structure has a different length because of the number of tests they've done.* I have created a variable in the aStudent structure so that i can know the number of tests a student has done...but don't know how to use it.
Public Class FormAdmin
Dim currentStudentName As String
Dim currentStudentID As Integer = 0
[code]....
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Jun 18, 2011
I have created a structure as below. I want the structure to be an array...so I can use a call like picks(1).a or picks.a(1) = blah blah. I don't understand how to use an array of a structure..
Public Structure apicks
Dim a As String
Dim b As String
End Structure
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May 22, 2011
what is the best way to add, delete elements from arrays of structures structure
vb
Structure Proxy
Dim Server As String
[Code].....
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Mar 14, 2010
I would be more that happy for someone to tell me I am missing something very simple here I am writing code that - amongst other things - talks to code on other servers using the tcpclient function in .net
What I want to do is - in essense very simply. I want to define a structure which includes an array load it with data and sent it to the other end of the socket.
[Code]...
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Jan 29, 2009
I have to make this program to keep track of product description, ID, price, and quantity. I am manually coding some and the user can input products as well. I want to display the product and it's ID in a listbox and put price and quantity in seperate labels. [code] My question is how do i keep the array index numbers sorted so when i click an item in the listbox it will show the price and quantity in the labels for them?
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Feb 16, 2009
i am currently running a program that will allow me to save all data on the form to open and edit at will. It uses a structure of 8 arrays, each with 16 values to save the information.
When i try to save the text into the array, it tells me that its a bad record length and crashes.
Here is the
Public Structure save_weekly
<VBFixedString(8)> Public dates() As String
<VBFixedString(30)> Public description() As String
[Code].....
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Nov 10, 2010
I have the following code... in an MDI application. [code] Various lines of code which put data into the Myinstance and then save the instance into the ArrayList.I have buttons which run procedures and functions in the formchild and also in the Class1. I need it so you can jump between formchild instances, and when you do so and click a button on that form, it will run the Class1 code but using the data in the arraylist and myinstance that was set previously by the selected formchild. Then if you switch to another child it uses data from this form. Can this be done by declaring the arraylist with more dimensions and then refer to the records with the index of the selected form instance, e.g.Selected Child is index(3)
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Nov 6, 2010
I have created an MDIparent form and a MDIchild. There is a button on the parent which makes multiple 'clones' of the child form, each time its clicked.I also want (maybe with a module) a set of variables, and array of a structure but these are available to each copy of the child, but each copy's variables, arraylist etc contain its own data?Therefore if you select child1 the variables and array will have different data to child2, child3...etc...
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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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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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Apr 12, 2011
I needed to create an app using arrays. The goal of the app was to input a certain amount of points and display their level of contribution and any benefits they receive (for example: enter 500 points -> display "Gold level" and "Fieldhouse privileges, Parking at game, Football tickets"). I was supposed to use a loop and intLevel array to find the donor level that corresponds to the input amount, display the donor level using the strLevel array and using the strBen array display the benefits that apply to this donor.
What I was given:
Dim intLevel() As Integer = {50, 100, 200, 500, 1000}
Dim strLevel() As String = {"Contributor", "Laker Club", "Bronze", "Silver", "Gold"}
[Code]....
My app works, but my prof's comments on it were to get rid of the "+ 1" on the first "Do Until" loop, cross off the second Do Until loop and he just wrote "not quite" next to the bottom two lines.
So basically, I'm wondering how I would write code to search for the amount of points (without having to add the "2000" so it doesn't blow up on me) and matching it with strBen. To be honest, I don't understand why I am not getting points for this.
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Jan 26, 2011
Lets say I want to create an array with 20 elements all set to a default value (let's say, 0)
But later, during runtime, I might want to resize the array. I might make it larger, to support 30 elements. The 10 new elements will have the default value of 0.
Or I might want to make my array smaller, to just 5. So I delete the complete the existence of the last 15 elements of the array.
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Jan 17, 2009
I am reading data from an excel spreadsheet and i want to create several arrays to save the data in (according to how many rows of data i have which is an unknow untill i actually read the sheet).
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Apr 12, 2010
being used to PHP and the easiness of creating arrays with no specific size... I'm hating arrays in VB.
Is there a way I can create an array who's size I won't know?
I'm pulling information out of an XML file and need the information available in another sub - so I'm stashing it in a public array I create at the beginning of the form.
[Code]...
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Mar 17, 2010
Basically the assignment says:Create an array that accepts user input. When the user inputs -1, stop the entering process.Check user input to circumvent bad numbers (numbers less than -1)Make two copies of the array (making sure the two new arrays are only as big as the amount of numbers the user input, might need a counter)Sort the first copy using any algorithmSort the second copy using standard array.sort method.Display all three arrays in a form.I have this so far, and I'm stumped as to where to go next.
asdf
Public Class SortingForm
Establishing Module-Level Variables
[code]....
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Mar 6, 2011
I have the followig problem; i want to make a class with a private field as a 2-dimensional array, where it's dimension is set in the constructor of the class.Contained data does not matter at this moment.I've looked a bit around but couldn't find a direct solution to my problem, is this possible in VB.NET? [code]
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Sep 19, 2011
having trouble understanding databases in visual 2010.
I have a database, which is loaded into a table adapter when the form loads. I want to assign each column of the table adapter into an array
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Nov 30, 2010
My problem is that i am trying to use a list box to display all the data from one column in one table of my database. and so, i dont know how to do that although someone hinted at using an array, i'm just not entirely sure how also when the list of data is displayed i aim to have a 'select' button that will take the user to the record of the selected item from the box.
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Jul 20, 2009
I'm attempting to create a list of structures that contains a list of structures. I can't seem to figure out how to properly allocate the object for the inner list of structures. I expect the outer list of structures to have a couple thousand entries and the inner list of structures to be fairly small at 2 to 10. Both lists will grow over time but the number of elements within the inner list will be constant for an instance of the outer list. Meaning, if an instance of the outer list has 2000 entries each of those will have the same number of elements on the inner list, say 4 entries.
Here is a simplified code fragment. This fragment makes no attempt to create the instance of the inner list "StructBlist" since I can't figure out where to put it. Tried "New List(Of StructB)" in the declaration as well as "Alist(0).StructBlist = New List(Of StructB)" but neither works.
Public Class Form1
Structure StructA
Dim FieldA1 As Integer
[Code]....
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May 9, 2010
In VB6 I load a recordset containg all of the records (6 fields per record)in a table into an XArray and then manipulate the records in the array and then write them back to the original table. The array issorted by the first field (1 to maybe 8000 or more) I need to find records in the array by an ID field and then move them (because of some external criteria that happens many times) from say number 400 to number 375. Then all of the other records between 375 and 399 were renumbered up 1 to fill the gaps left by the move.
The XArray worked well as it could find and also move to a next record easily to facilitate the revisions to each record quickly. Everything is done in VB6 in code and nothing visual needs to be shown to the user until say 2000 of these external changes are complete. What is the best, most efficient way to do this in the .Net framework in VB2010. Datasets, Dataviews. tableadapters, arrays. enums ?
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Dec 10, 2009
My assignment is to have a user enter in big integers using what i think is two parallel arrays. I got this far but now im stuck. I think i need to actually convert the text box input into an array but i do not know how to do that. I am all over the place in this project.
'Created/ Revised by: Jessica Falcetta
'Cap 204 Final Project: Big Integer Project
'Project Purpose: To calculate large integers through parallel arrays
[CODE]...
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Feb 2, 2010
I have a VB.net console app and I am opening a function in a dll written in fortran. I am passing 3 arrays through the function by reference. When they come back out the otherside they ahve all tunred to arrays of only one element And that element is 0.I read on the internet somewhere that when doing this kind of thing it is a good idea to only pass the first element of the array into the function.I tried changing my function declaration to accepting single elements rather than single dimensional arrays, and now the arrays are the same length before and after the function call, but they don't seem to be changing at all, so i'm not sure that this is working
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Oct 30, 2010
the statement Dim state(49) As String and maintain a list of certain states. The list of states should always be in alphabetical order and occupy consecutive elements of the array. The buttons in the program should give the user the following options: (a) Take the state specified by the user in a text box and insert it into its proper position in the array. If the state is already in the array, so report. (b) Take the state specified by the user in a text box and delete it from the array. If the state is not in the array, so report. (c) Display the states in the array. "
Private Sub states_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
state(0) = "Alabama"
[code]....
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Jun 21, 2010
I have a directory structure as follows;
ad_folder
--folderA
--folderB
--folderC[code]....
at I do not know the number of or the names of the folders, they can be different in different cases, I only have the root path.how I can display folder contents in VB.net and the code worked but couldn't figure out how to create the arrays and display only folders within folders starting with "ad_".
System.IO.DirectoryInfo and System.IO.FileInfo to be used for getting the folders.A literal control can be used to create javascript arrays in ASP.NET. These js arrays can then be used on the client side.
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May 3, 2010
I was wondering if anyone knows a built in method ( LINQ say or a LAMBDA expression or other way ) that you can compare2 arrays - collections that would be valid for an equivalent 3rd array - collection which is a combination of the 1st two.
As an example consider;
* * *
A L E
[code].....
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Oct 13, 2009
How can I sort three arrays so they are sorted together (the other two arrays are in sync with the first)?unsorted unsorted unsortedarray1]CODE]....
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Apr 25, 2011
I'm trying to develop 2 companion applications. One application will be a FileSystemWatcher service application that will create/maintain a database containing file metadata (file properties) from a specific folder structure on the user's C drive. The other application is executed by the user which contains edit boxes pertaining to the metadata. As the user enters data in the edit boxes, the code will execute an SQL statement which in turn will display a list of file matching the entered criteria.
I'm thinking about using Microsoft Access as the database since all users have it but I'm willing to use another database format as long as it something intrinsic to the Windows XP 64 bit system (i.e. I don't want to install another database application in order to utilize its database format). So, do you have a suggestion on a database format? Do you have some pointers or links, on how to create database file and tables on the fly? Should I use DAO or ADO or something else? I'd prefer to work in VB.NET.
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