Copy DataTable Derived From My Own Class?
Jun 18, 2008I have a derived DataTable[code]...
Overload resolution failed because no accessible LoadDataRow' can be called with these arguments.
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.net - Suppress A Property Or Method From A Base-class In A Derived Class?
Apr 7, 2011Supose a base class
Public Class airplane
Private var_num_seats As Integer
Private var_num_engines As Integer
[code]....
Obviously, I don't wish that the class Glider has the method "start_engines" neither the property "num_engines". Otherwise, other child classes may have. How can I supress these property and method in child class, not just ignoring (if I can)?
Access The Base Class Inside A Derived Class?
Oct 22, 2010How do I access the base class inside a derived class?
View 1 RepliesHiding A Method From A VB Class In A Derived C# Class?
Apr 20, 2011I'm writing a set of unit tests for a large, complex class called ImageEditor from a piece of legacy code, where image processing and GUI functionality isn't strictly divided. One of the methods in the class, BaseImageChanged, seems to be concerned entirely with how images get displayed and should be disabled in my unit tests to avoid unnecessary complexity. The test project is in C#, and the original code is in VB; my idea was to create a Decorator for the class in C# and then hide the method behind an empty one that does nothing. However, when I try running the unit test, the VB code keeps referencing the old BaseImageChanged method as though the replacement didn't exist. Here's what I'm doing:
(VB class)
Public Class ImageEditor
...
[code].....
Display The Rows Of A DataTable Derived From Other Other DataTables On Textbox (Typed DataSet)?
Mar 29, 2010I 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.
[Code]...
Copying A Class Into A Derived Class?
Oct 19, 2010I have two classes, one derived from another.
Private Class clsVehicles
Public Make As String
Public Model As String
[Code]....
.net - RemoveHandlers In The Derived Class
Mar 19, 2010I 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?
[Code]...
Set The Values In The Derived Class?
Apr 26, 2009I 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.
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Derived Class Shared Methods?
Nov 3, 2010I 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.
VS 2008 Base/Derived Class?
Jan 17, 2010Trying 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 -
[Code]...
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...
[02/03] Base Class Called PageBase And Then A Derived Class TestPage That Inherits From PageBase
Feb 4, 2009I have a base class called PageBase and then a derived class TestPage that inherits from PageBase. In PageBase I have overridden the OnInit() and when it is called and I inspect the value of 'Me', it is of the type of the derived class and not the base class. My question is how does inheritance really work? For instance, when instantiating TestPage does an instance of PageBase get created too?
Here is my code;
Partial Public Class TestPage
Inherits PageBase
Public Sub New()
[code]...
Create A Derived Class, And Identify The Inheritance?
May 8, 2010The test is base on Visual Basic inheritance, need to create a derived class, and identify the inheritance.
View 5 RepliesHide A Derived Method Of Base Class?
Sep 10, 2009I 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]...
View 5 RepliesUsing Derived Class To Satisfy Interface Requirement?
Dec 16, 2009I 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?
VS 2008 Same Interface, Base And Derived Class?
May 11, 2012I'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
[Code]...
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.
Use Derived Class Shared Variables In Shared Methods Of Base Class?
Jun 4, 2010I am trying to add shared members in derived classes and use that values in base classes...
I have base
class DBLayer
public shared function GetDetail(byval UIN as integer)
dim StrSql = string.format("select * from {0} where uin = {1}", tablename, uin)
end function
end class
[Code]..
currently there is error using the tablename variable of derived class in base class but i want to use it i dun know other techniques if other solutions are better then u can post it or u can say how can i make it work? confused...
.net - Derived Class Members Not Available When Added To Custom Collectionbase?
Apr 28, 2009I 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
Cancelling Button Click Event In Its Derived Class
Aug 29, 2011I 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.
View 1 RepliesHow To Avoid Writing Common Code In Derived Class
Jun 28, 2010I 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?
Override A Public Shared Method In Derived Class?
Oct 8, 2010Can we override a Public Shared method in derived class? If not why?
View 2 Replies[2008] Base Class Inherited By 2 Derived Classes
Jan 30, 2009i'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:
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Using Reflection To Attach / Detach Handler Of Base Event In Derived Class
Dec 13, 2009I 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.
View 2 RepliesCreating DataTable And Copy Existing DataTable Schema?
Feb 17, 2011I'm using vb.net 2010.I have a DataSet with a Table and data. MyDataSet1 which contains Table1 I want to create another table that is the same as the Table1 but without data, but it should have the columns, etc.
View 1 RepliesDesign Patterns - Inheritance - Do All Properties In The Derived Classes Have To Be Declared In The Base Class
Aug 8, 2011Background: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]....
Asp.net - Copy Data From Datatable To Dataset.datatable?
Oct 31, 2010how to copy data from datatable to table in dataset i ry this but its readonly property
ds.datatable1=newdt.copy
Derived Treeview Using Derived Treenodes
Dec 25, 2009I 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.
VS 2010 : UserControl MouseEnter/Leave Events Aren't Firing - Cannot Raise Base Event From Derived Class
Feb 18, 2011When i use my UserControl in a project my Mouse Enter & Leave events aren't firing, i assume i fix this with a raiseevents in my usercontrol. However when i try to do this it says something about "cannot raise base event from derived class".
View 7 Replies.net - Can A Generic Version Of A Derived Class Override A Base Method Using The Generic Type
Apr 13, 2012Consider:
Public MustInherit Class Column
Public ReadOnly Property ReturnSomethingUseful() As Object
Get
'return something useful
[code]....
But this gives the following error:
Public Overrides Function ParseValue(sValue As String) As Boolean'
cannot override 'Public Overridable Function ParseValue(sValue As String) As Object'
because they differ by their return types.
I accept that you can't do this, but I'd like to be able to preserve the semantics of what I'm. trying to do, which is to have an untyped version that deals with Object, but a typed version in derived classes that knows about the specific type T.
In The Derived Class - Have Lots Of Fields Defined - Prefered Style - Put 'em After My "new" Sub Or Before?
Apr 2, 2012I have a base class:
public class foo
public sub new(byref bar as foobar)
end class
and a subclass
[CODE]...
My question is: In the derived class, I have lots of fields defined. What's the prefered style? Put 'em after my "new" sub or before?
Get Type Of Derived Generic List Class From List Item Method?
Mar 23, 2011Public Class notifierMain
Public Class Contacts
Inherits List(Of row)
Public Sub New()
[code]....
When I debug this winforms application I get curType = "notifier.notifierMain+Contacts+row" I want to the Validate function to know it is in MyContacts. How do I do this?