Derived Treeview Using Derived Treenodes
Dec 25, 2009
I do have a customized treeView which inherits from treeview and uses customized treenodes which inherit from treenode. It works, but each inherited method of the treeview using a treenode as a parameter forces me to do an explizit cast from treenode to my customized treenode to access the additional functionalitiy of my treenode class.
Is there a general way to avoid explizit casting all day long? E.g. telling my customized treeview that all it's properties, mehthods, etc. from now on are working with my customized treenodes instead the general treenode as default?
Turning off option strict is not an option because I want to keep this. Overriding each method, etc. is to cumbersome.
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Mar 19, 2010
I use to set WithEvents variables to Nothing in Destuctor, because this will "Remove" all the Handlers associated with Handles keyword. Will this have the same effect for derivated classes?
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Apr 26, 2009
I have a base class where amongst other code I have declared 2 properties. In my derived class, I get data from the DB and assign the results to the base class properties. This is so when I go back to the base class code, I can access the property values. It allows me to set the values in the derived class but once I go back to the Base class, the values don't exist.
[Code]...
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Jun 18, 2008
I have a derived DataTable[code]...
Overload resolution failed because no accessible LoadDataRow' can be called with these arguments.
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Sep 21, 2009
I am developing a program in VB.NET. I have an enum called PriceType that is declared in a super class ItemPriceBase. There are 3 classes that derive from ItemPriceBase - ItemPriceMeasured, ItemPriceNDI and ItemPriceExtraCost. The subset of PriceTypes for these classes are totally unique from each - Measured prices are 1 to 6, NDI prices are 7 to 15 and ExtraCost prices are 16 to 22.
Is there a way declare the enum in the super class and then extend the enum in each of the derived classes so that they only have access to those options, yet I can still access a property in the super class that returns an enum of PriceType?
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Nov 3, 2010
I have a function that 2 derived classes use, but the third doesn't, would it make sense to just leave it in the base class, even though one of the 3 derived classes doesn't use it?The only way I could think of disallowing the third class is to basically create an intermediate class that is derived of the base, then the 2 that use the common function are derived off the second class.
Is it possible to prevent the 3rd class from using the function, while letting the two that are supposed to use it, use it?Does that just seem to go overboard, I mean as long as I don't "try" to call the function from the 3rd class, it shouldn't be a problem, I just was interested if there was a way to prevent it all together without a lot of hassle.
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May 20, 2010
I am finding that this may not be possible, but am trying to see if anybody has a solution.
I have four classes, two are core classes and two are those core classes extended[code]...
This fails because es is of type, extSecurity and the base class expects a type of coreSecurity. I've not found anyway to cast this to allow for me to override this base class in C#. In VB it works just fine.
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Jan 17, 2010
Trying to implement some sort of commit/rollback functionality in my base objects. I have it working with some help from google. However, I have a question My Base Class has a BeginEdit as shown below -
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Now, what I'm confused about is if I create another class, Class1, that inherits the base class. I add some properties such as Name, Age, Location, etc. to Class1.When I do Class1.BeginEdit, wouldn't "Me.memberwiseclone" make a copy of Class1, then CType try to cast it from Class1 to the BaseObject class? How does that work if Class1 has additional properties like the Name, Age..blah blah? Where do those gets stored in the Base class? I'm having a hard time wrapping my head around the concept...
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Jun 25, 2012
I have created an ASP.NET class derived from the standard WebControls.TextBox, with the intention of adding extra properties that will persist between post-backs. However, I cannot figure how to get the values in these properties to persist. I have tried setting the value of the properties into the controls ViewState as part of the PreRender handler, but the value is then not accessible in the Init handler on the post-back, because the ViewState has not yet been setup.
I could look for the ViewState value in the Load handler of the control, but if the page/usercontrol that is using the control asks for the properties value during its Load handler, the control hasn't yet reached it's Load handler, and it therefore not there.
[Code]...
In the end, the way I managed to get it to work was to use a <asp:PlaceHolder> control within the repeater, create an instance of my control within the ItemDataBound handler of the repeater, and then add the control to the <asp:PlaceHolder>... all done within the Init section (which fortunately I'm able to do).
As Andrew found out in this previous question you can end up in a chicken/egg situation, where you need to create the controls in the Init, but you won't know what controls you need until the Load.
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May 8, 2010
The test is base on Visual Basic inheritance, need to create a derived class, and identify the inheritance.
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Sep 10, 2009
I would like to inherit from the Data.DataColumn in order to produce a DataTextColumn. That means that in the derived class, I dont want to see the non-applicable AutoIncrement property and the like - all I want to see are properties that apply to string types.[code]...
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Aug 9, 2010
I want to have a single table that represents a person and have a number of other tables (such as Student/Teacher) use the Person table to store information related to a person. Unfortunately the entity framework doesn't seem to like it when I try to add an association between the Student or Teacher class and I don't understand why. The Person table contains a column called ParentEntityID, which equals either a StudentEntityID or a TeacherEntityID. In an ideal world I would like to be able to reference the Person table by going Student.Person.FirstName instead of Student.Entity.Person1.FirstName. The error .Net returns when trying to connect the Student/Teacher table to the Person table is:
Error 3007: Problem in Mapping Fragments starting at lines 265, 289: Non-Primary-Key column(s) [ParentEntityID] are being mapped in both fragments to different conceptual side properties - data inconsistency is possible because the corresponding conceptual side properties can be independently modified.
The actual database I am working with is a bit more complicated and has a number of tables connected to the Entity table, which makes my object model pretty ambiguous and was hoping to be able to clean it up a bit by using the entity framework.I am using VB.Net 3.5 in a web application.
Update...In an attempt to internalize the different types of relationships I can form, I have been playing with this simple example and have come up with the following possibilities:And the reason why I cannot make an association between the Student and Address table is because that relationship is not enforced in the database. If I wanted an association between these two tables I would need to re-think the design of my database. Is that correct?
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Dec 16, 2009
I have an interface (called IPersistentBusinessObject) with a required function that looks like this:
Function GetFields(ByVal fromDatabase As clsODBCDatabase) As enumSuccessFailure
In a class, I try to satify the requirement with the following:
Public Function GetFields(ByVal fromDatabase As clsDatabase) As enumSuccessFailure Implements IPersistentBusinessObject.GetFields
In this example, clsDatabase inherits from clsODBCDatabase. So I'd expect this to work since clsDatabase does everything clsODBCDatabase does and more. However, it does not work. The compiler complains that I haven't properly satisifed the interface requirements for GetFields. Can anyone tell me why this does not work?In slightly different but related example, I have an interface that requires a function called 'AddItem' as in:
Sub AddItem(ByVal objObject As IPersistentBusinessObject)
In my 'building' class, I attempt to satisfy this requirement using:
Public Sub AddItem(ByVal building As clsBuilding) Implements IPersistentBusinessCollection.AddItem
In this example, clsBuilding implements the interface IPersistentBusinessObject. So I'd expect this to work since clsBuilding satisfies the interface contract. However, it does not work. The compiler complains that I haven't properly satisifed the interface requirements for AddItem. why this does not work?
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May 11, 2012
I'm struggling here.. I know I can disable the warning manually. However I'm not sure if this would be the right way to go about this.
Here's my interface..vbnet Public Interface IPopulatingClassBase Property Identity() As Int64 ReadOnly Property Dirty() As Boolean Sub Populate_Class(ByVal RecordID As Int64) Sub Save_Class() Sub Reset_Class()End Interface
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PS In my example think of it as classes that populate with data from a database. The parent class would be an organization, and the derived class a location. Both populate and have similar functionality. The only difference is locations are an entity of an organization(the data record for a location constraints it to an organization) upon loading location data I also populate the organization class. This is a real example of what my project does.. so having said I just want to know how I can get around this warning, and if not would it have any consequences if I left it as-is.
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Apr 28, 2009
I have a Base Class, called primitive Graphics. derived from this class are several different types of graphics, squares, rectangles, lines, etc. I am storing those graphics in an object that inherits collectionbase. This causes a problem because I cannot access any of the members in the derived class when they are added to the collection. Here is the default property for my primitivecollection class
[Code]...
My current workaround is to just put all of the public members in the base class, however this is starting to look ugly as I add more derived classes that need members available to the derived class only
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Aug 29, 2011
I was working on a custom button, in which I had to capture the event of the button, and depending on the certain conditions, either I'll block the event or pass it on the form containing my custom button.[code]Now, I do not have any idea how to block the event and not allow it to pass if the users opts for "No" in the given example.
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Sep 8, 2009
A customer has provided me with a spreadsheet file his team uses to provide quotes for a product. The spreadsheet has extensive data in underlying sheets and calls those sheets as part of the numerous formulas on the quote sheet.
I've been tasked with web-enabling this tool such that the quotes can be generated on the client's website, hosted in a shared environment, running ASP.net 3.5 webforms. The quote web form will be in a Restricted portion of the website controlled by ASP.net membership API.
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Oct 10, 2009
Create ASP.net 3.5 web form application derived from Excel Workbook
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Jun 28, 2010
I am trying to minimize my code writing. I have DBLayer base class that selects, inserts, updates and deletes records from database. I need only fieldlist and table name from each derived classes to perform the actions. I have defined static tablename, fieldnames in derived class. Currently I am defining next static functions in derived class for GeneralSelect [which selects all records], GeneralInsert[Which inserts a records], GeneralUpdate[Which updates records as per given id] and GeneralDelete[Which deletes a record of the given id]. The parameter and all functioning are same just the differece is the table name and fieldnames.
One DBLayer Class that performs database actions
Class DBLayer
Public shared function Query(byval SQL as string) as dataTable
[code]....
... same goes for all other table objects... If I have 20 database tables i have to write getdata method in all 20 class changing only the tablename so i would like to get ride of it. So in order to get ride of it what do i need to do?
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Aug 4, 2009
I have created a strong name key file and run the gacutil to attach the dll to the assembly.. When i try to run the regsvcs bankaccounts.dll i get the following error...
Invalid ServicedComponent-derived classes were
found in the assembly.
(Classes must be public, concrete, have a public[code].....
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Aug 19, 2011
I have designed a small component I need to derive. The problem is one property from base class doesn't make sense in derived class, but won't hurts too (just it's ugly in property editor)
Now there is a solution to make that property non-derivable or hidden in derived objects?
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Oct 8, 2010
Can we override a Public Shared method in derived class? If not why?
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Dec 14, 2010
The following Code throws the InvalidCastException error. What I wish to know is why and what the standard workaround is for this situation.
Module Module1
Interface IFooBar
End Interface
Class Foo : Implements IFooBar
Public Shared Widening Operator CType(ByVal Val As Foo) As Bar
Return New Bar
[Code]...
What I would like is the line B = C to work without me having to know what type of object C currently is. I need to find a way to get this to work so that i can finish a function I ma working on so that it will excecute correctly on any new object which implements the interface and boasts an Operator CType function to cast it to the type used in the function.
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Jan 30, 2009
i've finally got round to learning about classes and inheritance, but i'm not sure how to proceed. i have a base class Employee, which is inherited by 2 derived classes. how do i use the same Employee class in both derived classes? obviously if i write a sub new for both of them + declare a new Employee class, they won't be using the same class. heres my Employee class:
[Code]....
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Apr 30, 2009
I'm calling a webservice that is returning an unknown quantity of images in the form of an a collection of byte arrays. (I can't change this) I need to display each image on a single aspx webpage. I'm currently using the Microsoft.Web.GeneratedImage control; [URL] to display the images.
[Code]...
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Apr 16, 2009
this code using an OLEDB source will populate the OutputColumnCollectionbelow it, the code using a flatfile source will not populate the OutputColumnCollection.
Why not?
Microsoft.SqlServer.Dts.Runtime.Application a = new Microsoft.SqlServer.Dts.Runtime.Application();
[code]......
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Feb 26, 2009
We use a custom collection derived from CollectionBase to store our Business objects
[Code]...
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Mar 29, 2010
I created a DataSet using the DataSources wizard. I can display the rows of each Datatable one at a time. But in this case, I needed to add a new DataTable (newDT) using the Add New Table Adapter control(?) on the toolbox. newTable is derived by JOINing three different existing tables (or, dataTable) in my DataSet designer. The query works fine and returns all the data as expected. Trouble, if I try to display the rows of the newDT on textboxes, I get a NULLREFERENCE Exception.
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Dec 13, 2009
I am just curious, if there is some way to attach handler to my derived classes base event, if I know EventInfo and I have Delegate to handler function. I have tried MyEvent.AddHandler(CType(Me, BaseClassType), MyDelegate) already, but no positive result at all. Consider being in need of attaching handler to custom event at runtime, while derived class possibly shadows this event.
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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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