Returning A Inherited Class As Base Class Type With Web Services?
Sep 25, 2009
I suspect I am being very silly here but I have the following setup
Class MustInherit myBaseClass
'some stuff
End Class
Class myInheritedClassA
[code]....
Running this results in the following error
Unhandled Exception: System.InvalidOperationException:
There was an error generating the XML document. --->
System.InvalidOperationException:
[code]....
is there any way of 'Widening' the inherited class to the base class so this would work?
EDIT:regarding XmlInclude(typeof inheritedClass), currently this method could potentially return a number of types of inherited class (i.e myInheritedClassA and myInheritedClassB) is it case of simply having to add each of the inheritedTypes in this tag?
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Jun 10, 2011
Suppose I have piece of code like this:
Public Interface ISomething
....
End Interface
[code]....
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Jun 2, 2009
I understand that inherited classes can't be converted from base classes. But is there any way to write a conversion sub, so that the base class gets assigned to MyBase, then extra properties are added?[code]...
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Jul 5, 2010
bare with me during this silly example. :-) Let's say I have a class like this:
Public Class Animal
Public iLegs as int32 ' Number of legs
Public bWings as Boolean ' Wings? Yes/No
End Class
And another class that inherits the "Animal" class and adds one more property:
Public Class ScaryAnimal
Inherits Animal
Public iScariness as int32 ' 0-100, how scary is it?
End Class
Now, if I have an instance of "Animal" with some values in it, and I decide I want to cast it to a ScaryAnimal for some reason, how do I do that without having to create a new instance of "ScaryAnimal" and copy each property value?Basically I'm looking for a way to do this, without having to write the lines marked with '*** below:
[Code]...
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May 19, 2010
The program below trhows an error in the line "mTable2 = mTable.Copy". The error is: "Unable to cast object of type 'System.Data.DataTable' to type InherintanceQuestion.InheritedTable". This is because mTables is an instance of the InheritedTable class which inherits a DataTable and mTable is a DataTable. So, is there any way I can create the mTable2 to the mTable.copy to the mTable.
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
[code].....
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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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Jan 16, 2012
In our application, we have a number of Windows Services (more than 30) that must run behind the scenes to process data at given times throughout the day. I was attempting to create a BaseService class that I could inherit from that would log to our database when the service started or stopped as well as some other common functionality. However, I ran into a show stopper in trying to create BaseService as MustInherit as we have a number of MustOverride properties. The issue lies in:
<MTAThread()> Shared Sub Main()
Our code is all in VB (as you can probably tell). Given that it is a Shared method, I cannot have it be overriden (i.e. make it MustOverride). Without this method, the code will not compile, however it will not really work in the base class. The code in this method is:
Dim ServicesToRun() As System.ServiceProcess.ServiceBase
ServicesToRun = New System.ServiceProcess.ServiceBase() {New BaseService}
System.ServiceProcess.ServiceBase.Run(ServicesToRun)
The BaseService (the name of my base class) cannot be created because it is specified as MustInherit. And therein lies my problem. I cannot create this in the Base Class and cannot override it in the inheriting classes.
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Jun 3, 2009
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?
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Apr 15, 2010
I have put this code in the global form Inherits System.Windows.Forms.Form. And then in the form that will inherit this from the global Inherits MenuStrip. "MenuStrip" is what the global form is called. But keep getting this error: Error1Base class 'MenuStrip' specified for class 'Lesson2' cannot be different from the base class 'System.Windows.Forms.Form' of one of its other partial types.
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Nov 23, 2009
I have a copy function that I'd like to override in subclasses to return the type of the subclass. Here are my interfaces:
Public Interface IBase(Of T)
Function Copy() As T
End Interface
[Code]....
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Dec 10, 2011
I have a parent class that is also a factory. For example:
Public Class Factory
Public Function clone() as Factory
' Some logic here
[code].....
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Mar 30, 2010
1) VB Allows non-type template parameters2) VB supports explicit specialization 3) VB allows the type parameters to be used as the base class for the generic type4) VB allows a generic type parameter itself to to be a generic 5) VB enforces that all codes are valid for all types of parametrs
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Oct 19, 2010
I have a base class (ex: Class1) containing a list of another base class (ex: ClassA). Each child class of first base class (ex: Class1AA, Class1AB,..) containing a list of child class of second base class (ex: ClassAA, ClassAB,...)The client must never know which child class is using, then i don't think i can use generic for my bases classes.I try something like this and many more, but i always received errors..Imports System.Collections.Generic
[code]...
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Jun 9, 2009
One thing that always bugged me, is that I do not see the base type in Visual Studio.I just stumbled on this, because I tried to cast a System. Windows.Forms.MenuItem to a System.Windows.Forms.Control..In eclipse the "intellisense" (or whatever it is called) shows me while exploring the members of a class for each member from which base class it is inherited.In Visual Studio I cannot see the base class, even if I use the Object browser or the help.[code]Is there a way to query the base type tree of a class at Design Time?
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Mar 12, 2010
When I do this
Public Class cInherits : Inherits Panel
I get this: Base class 'System.Windows.Forms.Panel' specified for class 'MenuButton' cannot be different from the base class 'System.Windows.Forms.UserControl' of one of its other partial types.
How do I inherit?
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Oct 29, 2009
I'm trying to force an inherited class to use a custom attribute. I'm creating a class library where the user who wants to create an item will do so, but be forced to add an attribute (or visual studio will automatically add the default attribute) to their inherited class. Here is what I'm hoping to achieve:
BaseClass.vb:
<CustomAttribute(10)> _
Public Class BaseClass
End Class
MyClass.vb:
[Code]...
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Oct 8, 2010
I have a project that has mainly two objects, both inheriting from a base. Like this:
Public Class Vehicle
Property Model As String
Property Make As String[code].....
The above function doesn't work because myVehicle is a Vehicle, not a Truck.Is there a way I can pass around a Vehicle type and have the IDE know which type to use? Or am I completely missing a better way to do this?
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Oct 1, 2008
I've been creating short test apps repeatedly to try to understand some of the concepts in VB.NET.For the most part it has been illuminating.I read Bucky's .NET knowlegebase tutorial on passing objects as parameters to newly created forms. He shows how to create a new class that inherits from the base form class and define a New() method with parameters Extending the concept I thought about doing the same thing with a form that was created at design-time (In this case Form2).
[Code]...
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Apr 22, 2012
Base class has one field to hold numeric balance value. With 2 methods that accept arguments for adding and subtracting the new input calculating new balance. Sub class has four fields dates, transaction, memo and amount.I have a deposit form, and withdraw form. Each time one transaction is entered it creates an object with sub class fields, then adds to the account collection. My problem is not understanding how to call the deposit/withdraw method and pass the current transaction amount back to the base class to alculate the new balance. Does anyone have any links to information/tutorials on how to perform something like this? As you can see with my code I have tried various different approaches without any success.
[Code]...
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Apr 7, 2011
Supose 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)?
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Apr 9, 2010
I am trying to create a class in VB.NET which inherits a base abstract class and also implements an interface. The interface declares a string property called Description. The base class contains a string property called Description. The main class inherits the base class and implements the interface. The existence of the Description property in the base class fulfills the interface requirements. This works fine in C# but causes issues in VB.NET.
[Code]...
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Dec 29, 2010
This is another one of my "I think it's not possible but I need confirmation" questions.I have a base class for a bunch of child classes. Right now, this base class has a few common properties the children use, like Name. The base is an abstract class (MustInherit)Technically, this means that everytime a child class is instantiated, it lugs around, in memory, its own copy of Name. The thing is, Name is going to be a fixed value for all instances of a given child. I.e., Child1.Name will return "child_object1", and Child2.Name will return "child_object2".
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Oct 22, 2010
How do I access the base class inside a derived class?
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Dec 10, 2010
If we are within the derived class then ofcource we can use MyBase keyword to access base class's object reference . That's fine , how can we take that base class's object reference outside that derived class's definition.My following code will explain what i want . Actually that is giving error right now, but it is explaining my requirement .
Public Class Base
Public x As String
End Class
[code]....
Actually there is error in ReadOnly Property BaseReference's Getter . Error is "Error 1 'MyBase' must be followed by '.' and an identifier. " how can i get base class object reference in Main method ?
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Jul 31, 2010
i have a class named fdetails and i do not want any other class to inherit from this classCan i set it to not being inherited by another class. I would like to get the things done in the following 3 languages
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May 23, 2010
i have a class named fdetails and i do not want any other class to inherit from this classCan i set it to not being inherited by another class. I would like to get the things done in the following 3 languages
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Jul 19, 2010
[code]The reason that this is a problem is that this is a collection of EventBase objects, but I'm trying to populate it with child classes instead. For example, I might have a JumpEvent class that inherits EventBase, and this is being put into the EventBaseCollection. That means that value.GetType() returns the type of JumpEvent, which as you might guess does not equal the type of EventBase.The goal of course is to simply loop through all of the various events without having to know anything about the sub-classes. Is there a way to determine the type of the base class so that the OnValidate call will work? Or is this just the wrong way to go about it altogether?
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Sep 11, 2009
Dim a as Type=GetType(className) would gimme the type. But I have only the name of the class as string. I want something like GetType("class1") which would return the type.
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Apr 21, 2011
I have extended an Entity Framework 4 entity class with a calculated property in a partial class. This member is not available on the client to which the entities are exposed via WCF RIA Services.when using C# appears to be changing the extension of the partial class file from .cs to .shared.cs. I tried this with my VB.Net solution (.vb to .shared.vb) and got a long list of errors. I believe what happened is that the partial class lost its association with the entity on the client - it inherited from object rather than EntityObject.
My best guess is that this is related to the way that VB.Net handles namespaces.Each project has a 'Root Namespace' which is prepended to anything that is defined within a code file. C# has a 'Default Namespace'which is the namespace into which new types are placed by default - via a namespace statement within the file.The partial class is probably having the client namespace prepended to it which puts it into a different namespace than the entity with which it is associated on the server.Is there any means of extending an entity in such a way that those extensions are available on the client via WCF RIA Services and VB.Net?
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Apr 13, 2012
Consider:
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.
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