[OOD] Class Design For With Database Back End
Feb 6, 2010
I was hoping that I could get some guidance from some of you guys on Object Design with Database back ends. I am trying to build what could be considered to be my first full scale application, which is a student tracker (simplification). While I have a reasonable idea of how I would go about designing the classes for the system, the bit that I don't know how to do is, how I would go about getting the data to and from the database.
For example with my other applications, I have done a couple of things;
1) Gathered all the data when the application started up, creating the objects then. Then when the application closed sending the data back to the database.
2) Have the code which deals with getting the data in the specific class, so the student class for example would take only one constructor argument which would be the studentID, then the class code would connect to the database and populate the object fields as appropriate.
3) Variations of the above. I have also looked into LINQ, which seems like it would be very useful if you don't expect your classes to deal with any business logic and just data, but I suppose it would be possible to create a wrapper class that would include the business logic.
[Code]....
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Mar 11, 2010
I was hoping that I could get some guidance from some of you guys on Object Design with Database back ends.I am trying to build what could be considered to be my first full scale application, which is a student tracker (simplification). While I have a reasonable idea of how I would go about designing the classes for the system, the bit that I don't know how to do is, how I would go about getting the data to and from the database
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Mar 8, 2009
I am making a program using Windows Form Application, and I had it set up in the design view. I double clicked a button to begin coding and up popped a ton of stuff in the code view that I had never seen before. I closed that, and somehow closed the design view by accident too. Now I can't get my design view back, even by re-opening the program (I didn't save), and double clicking the form to open it. It opens up as "Form1.vb" rather than "Form1.vb [Design]".What happened, how can I fix this and get my design view back?
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Oct 3, 2009
I reopened my project to edit it but it is only showing the code not the design I cant get it back how do I do it?
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Aug 10, 2010
how to organize the classes within my RPG project that I'm making. I've tried to implement a battle system but I am not comfortable with my initial results. This is the basic layout I currently have for my classes. [Code] clsCharacter contains statistics pertaining to one character, including magic available to that character to use. Also includes what weapons that character has equipped. clsTeam contains multiple clsCharacter, as well as a list of items that each clsCharacter in the team can use. clsBattle contains two clsTeams. One team is the player and the other is the computer. Now, this is a wonderful way to organize data. However, I see limitations with this approach. For instance, to pass data from Battle to Character, it has to pass through the team class and vice-versa. Plus, if I use Properties, it transfers data as ByVal instead of ByRef, so I cannot guarantee that I'm editing the original and not a copy of the passed object (IIRC)
In addition, I feel it is just messy code to include methods within the clsCharacter class that invoke this: MyTeam.MyBattle.DoAction(). Plus, the clsCharacter might not even be in the battle at the time - I don't won't to bog down that class featuring code that is exclusive for battling when I also need to be concerned about moving around the map, saving/loading data, etc. So, any suggestions? Right now, I'm burnt out of ideas. One idea I have so far is to include a function for the clsCharacter that exports a list of all possible moves the character could make, and if the character is CPU choose the most optimal one, and if Human than wrap it up in some nifty GUI so they can choose what action to take. But at the same time, how do I use that information within the context of the battle?
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Feb 20, 2010
Me need use MultiLineStringEditor Class from System.Design namespace.I add reference as file (as in the .NET tab, it no) from
c:Program FilesReference AssembliesMicrosoftFramework.NETFrameworkv4.0System.Design.dll
and Visual Studio show in References
System.Design.dll
.NET
0.0.0.0
False
<The system cannot find the reference specified>
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Aug 13, 2009
In the MVC design pattern we must use a controller(s) classes.
What are the fucntions (features) of the controller apart from handling communication bewteen Model and View?e.eg; can we include input validation code in the controller?
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Jun 3, 2010
I m working on an school management application, i design the database in access2003 and forms in vb.net2005. but i dont have any idea about the database conectivity. with the help of a book to connect with the db but i cannot save the data in the mdb file. in my application 1 add the followin buttons add new record modify record delete search using id or enrolment no.
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Jul 20, 2011
I can articulate my question well enough to get some clear and usable feedback here. I have reports (like paper reports) in my .NET application that have data bound to them. Typically the reports are a combination of many data elements across several busniess entites that may not all relate through an Inheritance hierarcy, etc. This makes it difficult to get all the needed data placed together to bind to the report.
So what I have done before are make 'Report' classes with data elements specific to supporting the reports they are bound to, and on the back end might be tied to specially created Stored Procedures that bring this data back (maybe several joins across many tables to get the right data needed). So if I was to make an analogy to the database world, I am essentially 'denormailizing' the data structure to get all of this data into a single class to make it easy to bind to the report.
However on the hard line OOP concepts and architecture design, one could say that a report is just another 'thing' to bind data to, and its class should not be designed just to suit the needs of data binding. In this thought process, I would actually need to make my class design be able to create the relationships needed to get all of the data together properly to still be bound, but not create any special 'Report' classes. I find this difficult to do sometimes. It is much easier to create these relationships in the back end stored procedures and then just output the resultset to be almost immediately bound to the report.
So what is the right way to solve this? If I create these specialized report classes with really no behavior, am I introducing an anti-pattern like the Anemic Domain Model?I could use some feedback, and please speak up if my question and scenarios did not make sense.
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Nov 19, 2010
can anyone teach me how to save data in microsoft access database and retrieving it back from database?[code]so, how do i save it in that and how do i load their data by typing their ic no only..
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Apr 22, 2010
I've got a BaseDataClass with shared fields and functions
CODE:
I have several classes that derive from this base class. The derived classes have all Shared functions that can be called directly from the BLL with no instantiation. The functions in these derived classes call the base Init(), call their specific stored procs, call the base CleanAll() and then return the results.
So if I have 5 derived classes with 10 functions each, totaling 50 possible function calls, since they are all Shared, the CLR only calls one at a time, right? All calls are queued to wait until each Shared function completes.
Is there a better design with having Shared functions in your DAL and still have base class functions? Or since I have a base class, is it better to move towards instance methods within the DAL?
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Aug 19, 2010
This is a followup to the question I asked here:
[URL]
I understand the answer in the post above, which is absolutely amazing, by the way. It's about implementing interfaces with a class. However, what if a class needs to share features with another class?Yes, that class can an Interface. However, let's use this sample definition.
[code]...
Or, in other words:An equippable item can perform acts outside of its typical usage of a shield or weapon. But not all items can act as a sheid or weapon.I mean, I could create a class that implements IWeapon, IShield, IMagic, IUseableItem, etc. But there should be a better way than returning NULL when those interfaces are called.
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Aug 22, 2011
I need a few threads working simultaneously with URL requests in a VB.NET 2010 app. Once one of them finishes, it should continue with the next task in a list. I'm new to using threads. Since it seems like I can't declare an array of BackgroundWorker, I thought I'd have a control class that creates an instance of a task class for each task, which in turn starts a BackgroundWorker in its constructor.
However, with this approach I'm not sure how to report the result back to the control class upon completion. I had this vague idea that I could send a reference to an object in the control class (or to a public event I can trigger, is this possible?), but then I have to somehow store this address until the work is done. And I don't know how I can store the address from a ByRef for future use.
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Aug 2, 2010
Let say I have a function inside a class which require 4 parameter (table name,field name,field value, return field) When I use this function my form, such as
myclass.Search("customers", <-- after pressing the "," a popup list will be displayed that contain all the fields in "customers" table.
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Oct 16, 2011
in VS 2008, is there a way to design a ContextMenuStrip in a designer without a relation to a specific Form or UserControl class? For example,if you need the same ContextMenuStrip in Form1, Form2 and Form3, in which of them am I to design the ContextMenuStrip? Do I have to add a "pseudo-Form" to the project that contains my shared ContextMenuStrips and create only one instance of that Form, or is there another way? I consider this a programmatic hack, that's why my question is whether the IDE offers something better.
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Oct 6, 2010
I am in the process of prototyping a small sockets application, which monitors IT infrastructure (due to in-house financial and deployment restrictions, I am unable to utilise an existing commercial or open-source solution). Basically, I have a server application and associated agent process for communicating heart-beat data to the server. The server application implements a TCP socket class (TCPDevice), which is called from a WinForm. I am aware of the restriction on updating the UI from processes running on separate threads, and that the preferred technique for acheiving this is via the use of Delegates in conjunction with the Invoke method. Having had very little need previously for using Delegates (apart from of course std windows events and the BackGroundWorker control), I am at a loss as to how to do this in the context of my application, and would appreciate some assistance, although it has occurred to me that I could use the backgroundworker for marshalling updates to the UI.
Eventually the application will need to update a grid of devices via feeds from the defined agents, however for the purpose of this exercise simply updating a status bar on the UI will suffice. The section of the code which I believe is relevant to propogating the code to the form is contained in the OnDataReceived method.Below is a code excerpt from the protoype app which should put the above into appropriate context:
Code from the form:
[code]...
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Aug 8, 2011
Background:I have a base class and several inherited derived classes. The derived classes don't always need to have the same properties. If any properties are shared among the derived classes, those properties would live at the base class level ('Contents', for example).Similarly, GoodDocument below has 'GoodThings' but would not want/need to have 'BadThings'.I want to treat instances of both 'GoodDocument' and 'BadDocument' as type 'Document'
public mustinherit class Document
public property Contents as string
public sub new()...
[code]....
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Jan 11, 2012
Need a procedure in SQL for translate a datatable in English to Arabic .I am having English table which is having category ID ,Code etc upto 25 columns in the SQL Database.We want to translate this table to arabic when user opts for Arabic .So need a procedure to convert this English table to Arabic.Do i want to use google translator for this case . Then how will it is linked with database .
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Mar 22, 2012
The main purpose of the my app that I need your help with is, to deliver an always (or close to) up to date a list of files for the user to choose from for a variety of common purposes. For instance, opening the selected file in its native client editor application so the user can make changes. Another purposes would be to print the file, and I have others.
If nothing else (meaning recommendations for a better design that still keep my desired in mind) I'd like ideas on how to update my complex DataSet (background processing options, what's the most efficeient/quickest way to update my DataSet) as the list of files changes while my app is running and my app is designed to never close due to the long amount of time it take to load it initially.
The list must be always kept up to date while my app is running because not only the intial loading of data takes a lot of time but updates (new/modified/deleted) could potentially take too long depending on not only how much data to update/add (new files) but how efficeient my code is in updating the list. To be perfectly clear: If a new file is created then it need to be somehow (automatically preferably or manually i.e. button code) add to the list. If a file is deleted then it needs to bet removed from the list. And if the file has changed, perhaps some of it metadata or thumbnail image have changes so update the file's data in the list. All of which (new/modified/deleted) need to be as real-time as possble without degrading the server too much and without the user waiting more than a handful of seconds.
Listing all the files as quick as possible whether that be with or without metadata initially is very important because most of the time the user is going to filter (or scroll the list by typing) for a partial file name. Once the user filters/scrolls to the desired file there's a very good chance that he/she isn't even interested in the metadata, most of the time the user wants my app to open the selected file in its native client editor application so he/she can view or modify the file. The initial
load time of the data doesn't concern me as much as updates because the user can possibly do other things while it initially loads all the data as long as it not too long (more than a few minutes). From there the updates will either be automatic if possible (most desirable from a users standpoint) or the user initiated (e.g. button). Plus I'm thinking the updates might need to be done with a few different background processes (multiple threads) because I think I need one for periodic updates (e.g. every
15 minutes) and one background process for page updates meaning whatever the user has either scrolled to or filtered for, more accurately all files currently display to the user will be systematically update in the background so the user can still operate my app.
I'm currently using SqlDataAdapter.Fill to fill a DataSet object variable (which is bound [BindingSource] to a DataGridview control) to first populate the DataSet from the SQL query and then prorgammatically adds records (DataRow) for local files but please make recommendations. I don't mind big changes or starting over if necessary, I just want the best app possible based on the aforementioned criteria. I'm not sure if it complicates matters but I've also added custom columns in the DataSet for some special needs (thumbnail of files, booleans for tracking custom statuses). For the local files I'm currently populating the DataSet prorammatically (iterating a path/file string collect made by System.IO.Directory.GetFiles) since the list is first (and very quickly) populated with Vault files (which is always a far larger list than the local files) so . Again, I don't have to take this direction, make recommendations.
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May 18, 2012
i try using both detail view and form view but they are not flexible enough to place my picture where i want it
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Mar 12, 2012
I've been studying design patterns off-and-on now for a project I've recently been working on. I've been fortunate with this last one not to have to work with databases, but will soon have an opportunity.
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Mar 29, 2011
I am developing an "AddressBook" like project in VB.NET. While developing database in SQL Server2005, i want to follow the principals of normalization and keep its degree of normalization as high as possible. Fields i am using are these.
Create table AddressBook_Contact
(
Contact_ID int Primary Key,FirstName varchar(15),MiddleName varchar(15),LastName
[code]......
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Jan 28, 2010
i have a form and i want to have my form to have a button thatwhen i click the button a backup of database will firedo you have any solution or idea for this
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Jun 21, 2009
[code]So both methods seem to step through fine but don't commit the changes back to the database. This function is my only 'edit' function. It needs to look for the datarow which is to be edited. Edit it and then save the changes to the database.My other two functions create datarows and work fine. This one I just can't work out. I have a dataset with two datatables. This is running as a web service. Database is MSSQL.
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Nov 30, 2011
I am strugling to get a value back from an access database, what i am using is,
Public Shared Function ReturnTimes(ByVal DateValue As Date) As DataTable
Dim cmd As OleDbCommand = New OleDbCommand()
With cmd
.Connection = Database.conn
[Code]...
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Jun 27, 2011
How can i take back up on Every minute and hourly and complete whole day backup using VB.NET i.e i want to know the coding example
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Dec 12, 2009
I have an mdf file in the vb.net 3.5 project I am working on. I wanted to write an stored procedure that will create a back up of the db in a selected location. How can I take a back up of the database from my application? I want the user to take a back up of the database manually.
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Mar 31, 2012
I am designing a database using access 2010 and I ve been asked to design the user interface with Visual basic.I actually have designed tables and their relationship and did some queries according to the requirements. how do I create user interface in VB from this point knowing I don't have any form and report designed in access?
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Nov 6, 2011
There exists a database that holds information on each planet in the solar system. The database has multiple tables.The program intends to access this data to display it to the user in a variety of manners. The program does not intend to manipulate the data at its source, though calculations on two fields may be performed to determine certain display characteristics.What is the optimal method for accessing the data?My initial approach, (read: gut feeling, no research) was to take each related row of data from the database and create an object of a custom class based on the data. So you might wind up with:[code]Then use these objects to perform whatever actions the program needed to. I ran into a lot of problems trying to implement this, so that I believe my design approach is fundamentally flawed.
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Sep 14, 2011
I am looping through a database with pdf locations. The application is button click event driven. The problem I am having is that I display a pdf. If the user clicks on the button then the pdf information is inserted into a database and the loop should be taking me to the next pdf. However, this loop does not seem to give what I need. What ends up happening is the first pdf gets displayed twice. I think mainly because I display the first pdf onload, but when I click the button it agrees and grabs the first item from the database. And it ends up falling behind because its restarting the query and I cant quite figure out how to get the button to catch the first displayed pdf, or skip it entirely since I am using a welcome pdf. So on the welcome pdf that is supposed to be displayed initially the user clicks agree and it agrees to the welcome pdf instead of just skipping it. I am not quite sure how to just move past the pdf.
public sub onload()
display the welcome pdf
end sub
[CODE]...
Now if I run the code without the loop it works fine. I just end up having to run the app however many pdfs I have in my database.
query data
display data
insert data
Windows.Forms.Application.Exit()
To display pdfs I imported the com control for adobe so pdfs get displayed like this:
axacropdf1.src = my.mysettings.default.readpath & pdflocation
pdflocation is passed from a query fill.
I think I have an underlying design issue which probably precedes the loop.
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