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:
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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
Sorry if the title isn't very clear. This is a VB.NET (2010) question I have a superclass called "Device" which has a number of subclasses that inherit it. Some of those subclasses also have subclasses. In particular, I have a class called "TwinCatIntegerDevice" which inherits "TwinCatDevice" which inherits "Device."The relevant parts of Device look like this:
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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.
View 3 RepliesWhat is the proper design pattern for custom events in .NET (VB or C#).
I am refering to custom events, where in you override the AddHandler, RemoveHander, and RaiseEvent methods.
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.
View 8 RepliesI'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.
With C# anonymous delegates, we can avoid declaration of extra method, I know in VB.NET they're not available, but is there a design pattern that I can use so that I can avoid writing an extra method each time? I need it for SPSecurity.RunWithElevatedPrivileges which will be used a lot of times in our code.
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Suppose I have two events:
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?
View 3 RepliesI 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.
<?xml version="1.0" encoding="utf-8"?>
<ActivityItem xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<UserID>26</UserID>
<FormTitle>frmCustomer</FormTitle>
[code]....
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?
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.
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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
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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?
View 4 RepliesI've got a method I'm trying to translate from c# to vb, goes something like this .. x.For(typeof(IRepository<>)).Use(typeof(Repository<>)); VB doesn't seem to like the idea of a IRepository(Of ) ... what's the syntax on that?
View 1 RepliesI am writing a .NET DLL to iterate through all controls in the a VB6 Form passed byref.So far it seems to work VB.NET code:[code]but the TypeOf operator does not work. Is there another way to find the type of control?
View 2 RepliesWhat's the difference between "typeof" and "getType"?
View 3 RepliesI am trying to write code as the following-
For Each ControlObject As Control In Me.Controls
Select Case TypeOf ControlObject
Case TextBox
[code]....
But it says that "Is expected" after the second line. Is there any technique to do it?
Given this example:
Public Class Car
End Class
Public Class Vovlo
Inherits Car
End Class
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where Car.CubClass is either a Volvo or BMW if the car object has a subclass, or a car if it do not have a sub class. The problem is how to get the Car.SubClass.
I have subclassed the ASP.NET Panel control to customise the rendering of the GroupingText. However, while it appears fine in the final output, it is not appearing correctly in the designer. A sample of what I am doing follows: Is there anything else I need to do to make it appear correctly in the designer?
Imports System.Web.UI
Public Class CustomPanel
Inherits Panel
Public Overrides Sub RenderBeginTag(ByVal writer As System.Web.UI.HtmlTextWriter)
Me.AddAttributesToRender(writer)
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switching back to the code causes an error dialog to pop up with the message:"An error was encountered during code generation.The changes you have made in the designer have not been committed to the source code.it is recommended that you close and reopen the source file.The error message follows: Error HRESULT E_FAIL has been returned from a call to a COM component."The source code the Designer
View 2 RepliesI am trying to override a property of a subclass of an inherited base class. I've tried to simplify this code as much as possible but am not comfortable enough with my own abilities to simplify anything else without loosing the ability to understand an answer.The property propertyName in the otherClass is currently incorrect. I want to be able to override propertyName in baseClass with the propertyName in otherClass. Is this possible to accomplish?
Public Interface interfaceName
Interface iInterfacePropertyName
Enum enumName
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I'm developing this Usercontrol and I want it to capture theParentForm 's WM-Messages.I know how to just Subclass a Form, from the Forms code. Like:[code]But how do I do this from the Usercontrol? In VB6 I would have used code like:[code]All I want is to capture messages from the ParentForm's Window.
View 5 RepliesIn VS2010, targeting Framework 4.0, I have a UserControl which contains a TableLayoutPanel with an empty second row.Is it possible to add items to this second row using the Windows Forms Designer, or do I have to do it all via code?
EDIT: In reply to Hans Passant's comment, the linked question references a UserControl being used inside another control.I am asking a question about inherited controls.I have created the following test code, where TestControl is a UserControl containing a TableLayoutPanel named "TableLayoutPanel1":
Imports System.ComponentModel
Imports System.Windows.Forms.Design
<Designer(GetType(testDesigner))>[code]....
creates a control which, when viewed in the designer, contained a TableLayoutPanel named "TableLayoutPanel1" which is not designer-editable.Creating a new UserControl, not inheriting from either of the previous UserControls, and then placing a TestControl into it creates an instance of TestControl with a Designer-editable TableLayoutPanel named "TestControl1.TableLayoutPanelX".Is there any way to make the TestInheritedControl class, shown above, Designer-editable?
we changed the mapping from the table per concrete class to the subclass strategy and now the UnitTests fail, but I cannot recognize why.There's one base class Article and a child one SemifinishedArticle with no specific properties.
Article.hbm.xml:
<?xml version="1.0" encoding="utf-8" ?>
<ibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
[code].....
I'm trying to capture the initial value of a listbox immediately after it's clicked on, and before the SelectedIndex is changed. The following was taken from: MouseDown in WinForm ListBox Kills SelectedIndexChanged, converted to VB. The ListBoxComponent Class is in a Component that shows at the top of the Toolbox.
Public Class ListBoxComponent
Inherits ListBox
Public Const WM_LBUTTONDOWN As Integer = &H201
Public Event PreSelect As EventHandler
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I have a base class, "B", which has two constructors, one with no paremeters and the other that accepts one param, an integer. I have a subclass, "S", which inherits from "B" and does not define any constructors in it. I create an instance of S, attempting to pass to the constructor an integer.
I get the error: Error 1 Too many arguments to 'Public Sub New()"
This surprises me because I thought that if a constructor is not defined in the subclass, S, that the base class constructor method, specifically, the one with the single integer param would be invoked w/o an error. why I am getting this error? Are constructors a special case?
I have created my webpage in asp.net in 1024*768 resolution, my problem was that when i change my monitor resolution then the controls in my webpage will be displayed in unmanaged manner .
How to arrange items in my webpage which support multiple resolution ...
Whatever the resolution of my monitor the controls in my webpage will display as it is as managed in 1024*768 reolution !
In re-engineering a windows forms application, I find that a lot of code-behind in the various form classes is duplicative and I'm trying to centralize as many procedures as possible into a base class which can be inherited and used by the subclassed forms.
This process seems to be going well and is making the code in my subclasses much simpler and hopefully easier to maintain, but I'm not sure where to draw the line between leaving code in the subclasses and engineering for generic resusability and moving it to the base class.
Specifically, in some subclasses I have code which manipulates variables and objects specific to the subclass, and although I could move the code-behind into the base class, the base class code references specific objects which are needed to compile. For example, each subclass manipulates a databound datagridview and form detail controls which allows the user to select between multi-record and detailed single-record views of a datatable.
In Visual Basic 2008 do I need to declare dummy data objects in the base class so that the base class will compile? Or is there a way to indicate that the data objects will be provided by the subclass?
I seem to have reached a limit on the size of the form. I cannot make the form longer and I need to add more fields. Is there a limit on how many fields can be included in a form?
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