Lifetime Of Multiple Instances Of An Object / Design Pattern?
Sep 5, 2009
having difficulty with understanding object lifetime / instantiation.I have a windows from with a datagridview and a panel. The datagridview has a checkbox column and a list of names which is populated from a database.The panel has a few text boxes (e.g. name, age, favourite sports team) and a 'save changes' button.
The idea is that when the user selects a person in the datagridview by checking the appropriate checkbox then the panel shows the relevant data for that person (name, age, fav sports team) by pulling the data from a database. If the user would like to update the person's details they can do so by typing in the textboxes and then clicking the 'save changes' button. All quite simple so far.
The way I have designed this is to have a 'panel' class and to create an instance when the user checks a checkbox.(NB - the reason I have created a 'panel' class is that I intend to replicate the datagridview and panel on other tabpages within my form and thought it would be useful to have a generic 'panel' class that I could re-use.)
My code looks a bit like this:
If CheckBoxClicked Then
Dim UpdatePanel As New UpdatePanel(MyForm.NameTextBox, MyForm.AgeTextBox, MyForm.FavSportTeamTextBox, MyForm.SaveButton)
UpdatePanel.GetData()
...
When the user clicks the SaveButton the data is updated to the database and I have a display message (simple textbox) which says "Update successful" and displays for 5 seconds before hiding itself.
Here is the problem:Suppose a user checks a checkbox, reviews the data and does not make any changes, and then checks another checkbox and decides to update the data by clicking the 'save changes' button. What happens is that the "Update successful" message is displayed twice.
I think this is because every time the user checks a checkbox an instance of UpdatePanel is created. If a I select five different people using the checkboxes and then hit 'save changes' I get five "Update successful" messages.
I am not sure how to overcome this. It feels like each time a checkbox is clicked I need to check if an instance of UpdatePanel exists and then destroy it. I tried using UpdatePanel = Nothing and also investigated IDisposable and GC.Collect() but with no luck.
I have a project that uses regex, and while matching strings and regex syntax is working well [If rx.IsMatch(test) Then], i'd like to know (if any) a way to use regex to extract all instances of a pattern.
Using VB.Net, I'm looking for best practices in dealing with the following idiom:[code]What I really want is something VB.Net doesn't offer -- additional and simultaneous iterators on For Each statements.[code]I'm interested in both Linq and non-Linq recommendations, comments about Copy method design, comparisions to C# or other languages.
I am working on a parser for a serial data protocol. I have an overarching Packet class, a couple sub-classes such as CommandPacket and StatusPacket, and then a few sub-classes of each of those:
[Code]..
While I don't think it is entirely relelvant to the discussion, I am doing this in VB.NET. There is also a similar (but not quite the same) question posted here: Java - subclass validation design pattern
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.
I'm trying to replicate a design pattern used in a graphical programming language called LabVIEW. One thread produces commands, and another thread, or series of threads, consumes the commands.This is very similar to using Queues in VB...but there doesn't seem to be an easy way to start the consumer thread when new items are added to the queue.
Here is what I would like to accomplish, please let me know if there is a straightforward way to accomplish this with out of box .Net functionality.1) Start the Consumer Thread...it sits idle, waiting for some new commands to appear in its Queue.2) Producer places a few commands into the Queue. Example: "Home X Axis", "Home Y Axis", "Initialize Pump", "Display Ready Message"3) Consumer thread 'wakes up' at seeing the new commands, then performs the 4 tasks specified in 2.4) Consumer thread goes 'idle' again, and simply waits for new commands to appear in the Queue.
Process can continue on and on forever. The main problem I see with Queues is that there is no 'Wait for Something to Appear in Queue then Retrieve it" functionality. I don't want to use a perpetual loop to keep checking ever n milliseconds.
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Public Sub Control1Updated() Handles control1.TextChanged control2.Text = SomeFunction(control1.Text) End Sub
[code]....
Basically the pairs of {control1.Text, control2.Text} and {control2.Text, control1.Text} should be the same. If control1.Text is changed to let's say "a" then control2.Text is ALWAYS "b". If control2.Text is changed to "b" then control1.Text is ALWAYS "a". How do I achieve this with events without going into an infinite loop? [the best I can think of is to make a check if the other control.Text is already the desired value].
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?
In teh MVC design pattern, Controller is strongly related to the view (GUI). IN my application i need to generated a new BrandID, i used stored procedure to retreive the highest BrandID from teh DB (The model calls the stored procedure and sends the retreival value to the Controller), then in the controller increments the BrandID by "1" to create a new brand ID. SInce, controller is strogly related to "view", should i include this "brandID increment" part in teh controller or in the model classes?
I have a winform which allows people to edit data from a database, to simplify things assume there is a Customer table in database with 3 fields - Name, City, Country. Through winform(s) people can Add/Edit/Delete customers.For each of these actions we need to save:
What the field names are (Name,City,Country in this case)What the field values were before they were modified What the field values are after they are modified.If the action is Add or Delete then 2 and 3 will be the same.I have already implemented this using XMLSerialisation (but not using any of the design patterns) and my XML output looks like this.
The solution can handle different areas of the system with different number of fields (i.e the same thing works when you are modifying Products for instance).is there a well defined design pattern to deal with this kind of behavior?
Assume you have controls A, B, C, D and E all with a Visibility property. You also have states 1,2,3,4,5 and 6 in which various combinations of your controls would be displayed. Currently this is being handled by switch statements for each state: i.e.
Select Case PageState case "1" a.visible = false b.visible = true
[code]....
As you can imagine, this becomes a pain as every state needs a show/hide statement for each control. How can I refactor this so that adding controls and/or states becomes trivial?My first instinct is to extend the control and add a collection of states that it should display for but this sounds like overkill.
Edit:I was deliberately vague in my question in case this has other implications. In my current instance the "controls" in question are ASP Panels. Does that change anything?
One of the problems that I constantly see with Winforms applications is that the GUI thread is stuck while a long-running task is running or just plain stops refreshing (yes, I know - needs threading). Is there a code template/design pattern I can use when reacting to mouse clicks or button presses? Should there be a processing thread always running in the GUI app? Basically, how do I write a great Winforms Application that is easy to maintain and doesn't have any quirky refresh bugs?
I searched codeplex and google. I have found so many such as tustena but unfortunately they are not domain driven based and in these solutions I could not find a good modelling documents or references. i am a newbie in CRM but I am sensetive to design it with solid object-oriented fundamentals. Any reference or open source solution especifically for CRM design and implementaion in .NET? Cheers
I'm trying to figure out the lifetime of the tmpTabPages in the following bit of code. Lets assume the form has an empty TabControl named MyTabControl, that there's a collection of strings called NameCollection.
I'm trying to create 3 instances of the the Workshop selector form for the 3 individuals that I have inthe listbox to appear when I first run the program.
dim object1 as new clsDatadim object2 as object object2 = getobject("object1") "getobject" function is my "needed function"
the purpose is to set object2 to have same memory address with object1 so if i change the properties of object2 then the properties of object1 also changes..
Any best method of managing multiple SQL connections .net (VB). My application connects to four instances of SQL Server (2000, 2005, 2008, 2008R2) restoring databases, modifying data and taking backups. In addition to managing databases the app also has its own DB (on the 2008 instance) for storing various data. I'm using two methods to connect to the instances, SMO (For backups, restoring and retrieving information about the databases, size etc) and SqlClient for querying each database for many tasks such as updating fields and executing sql scripts.I have multiple forms for performing various tasks so there are many places I'm opening / closing connections.
Would it be best to maintain a persistent global connection to each instance from the application? (Two in total, one for SMO and the other for SqlClient) or open close a connection for each task I'm performing?) I'm not using LINK as I need the tasks to be as fast as possible. The connection string will differ on each connection (Based on Instance and Database being connected to) how would I manage this? A string in the config file for the applications database would make sense, as that would be static but the databases being worked on will vary with each connection. Currently I'm creating a connection for each instance within the main form:
Dim 2000Connection = New SqlConnection("Data Source=" & SQLServerName & _ "SQL2000;Initial Catalog=Master;User ID=sa;Password=P@ssw0rd;Pooling=True;") Dim 2005Connection = New SqlConnection("Data Source=" & SQLServerName & _ "SQL2005;Initial Catalog=Master;User ID=sa;Password=P@ssw0rd;Pooling=True;") Dim 2008Connection = New SqlConnection("Data Source=" & SQLServerName & _ "SQL2008;Initial Catalog=Master;User ID=sa;Password=P@ssw0rd;Pooling=True;") [Code] .....
I have the following problem. (VB.Net 2008)I have created a class (myFirstClass). In this class there are a lot of calculations being made wich gets fired by events in that same class.Now i want that same class to be able to fire more instances of itself. However i noticed that each time i fire an event from a Sub the program waits till the event is finished before going to the next line of code. This is a problem since i want the event wich fires a new instance of the class to fire it and forget about it.
I have two forms in my application. Form 1 is a listview that is populated with unique Customer IDs. When the user double click the listview on the particular Customer ID then it loads Form2. Form2 has many listviews within it such as a listview for the Customer telephone, another listview for their addresses etc and all the data presented in Form2 listviews are based on the Customer ID that the user clicked in Form1.
So here is my question...I want the user to be able to open Form2 with that particular details of the customer but also to go back to Form1 and double click another Customer ID and opens Form2 again (such as replicating Form2) with the other Customer details.So the moral of the story is i want the user to be able to have many instances of Form2 open each time they wish to view a different Customer ID without having to close Form2 down every time.
My ultimate goal is to get a list of PIDs and have a user select 1 of them.For example: the process image name is program.exe. The application name varies for each instance the program.exe is run, and therefor each application name has its own PID associated with it. By application name I mean the Task name under the Applications tab of Windows Task Manager. Another issue I face is that some systems run x64, so the name is no longer program.exe but program.exe*32
So my issue is, how do I search for program.exe, or on x64 platforms program.exe*32, and if there are multiple instances of program.exe/program.exe*32 running, how can I get a list of PIDs for each and associated them with the application name as the Task name under the Applications tab of Windows Task Manager.that might sound a bit confusing! So if it is, please let me know and I will try to explain more. Any reference guides or example code would be greatly appriciated as I have only used the "System.Diagnostics" but once.
I have written a base class from which I wish to derive several child classes (in this case Windows Form classes), and I'm using a Factory pattern in order to maintain a collection of the child instances, so that a form can only have one instance per primary key value. (sort of a mash-up of Factory and Singleton patterns.)
I'm using the following code in the base form class[code]...
this is probably something I should know, but I'm puzzled by this.I'm trying to create some objects and being able to access and modify these globally. I tried to create a Public Module and declare a few objects in this.I am able to access these from another sub, but I get an exception error when after building and runing the process and trying to modify these object. The same thing happens if I declare the object in the Public Class Form1. For example like this:
Public Class Form1 Public appWord = New Microsoft.Office.Interop.Word.Application Public wordDoc as Microsoft.Office.Interop.Word.Document
I have a control which consists of a couple of labels and a couple of buttons side by side.I want to add multiple instances of this control to a panel.The problem I have is with positioning/formatting.Whenever I add the control it just gets added on top of the previous one.Should I be using something other then a panel? Are there any tips ot tricks I should be aware of ?
How can I check for multiple instances of my visual basic application? When the user runs the application, I want to know how many instances are already open.
I have an application which the user can open multiple instances on the same machine. However, a section of the app would have sync problems if more than 1 instance has control over it. This is where I thought of transferring control, or sharing, between them. What should I be looking into?
They would have to be able to identify which one of them has control and to send text information over. I thought IPC or Named Pipes could do the trick, but I'm unfamiliar with them and examples seem to indicate only a single server will work. Here, I have multiple instances of the same app and every one of them needs to be able to listen for that request for control.
