Generic Mustinherit Class - Receive: "Type Argument BaseObject Is Declared 'MustInherit' ?
Aug 23, 2011
i have 2 mustinherit classes where one is a generic one:
'Visual Basic 2008 - .net 3.5 - Any CPU
Public MustInherit Class BaseObject
End Class
Public MustInherit Class BaseObjectList(Of T As {New, BaseObject})
Inherits List(Of T)
End Class[code]...........
i receive: "Type argument BaseObject is declared 'MustInherit' and does not satisfy the 'New' constraint for the type parameter"users would never enter data in the wrong form,files they choose to open would always exist and code would never have bugs.
I've got an Interface that dictates classes that implement it to use a large amount of properties and a few methods. I've been using this interface for some time and I have a large amount of classes that implement it.
Now, I need the interface to become a MustInherit (abstract) class, because I need to implement a single method that must be the same for every class implementing the interface (I mean the implementation must be the same, hence I cannot use an interface anymore).
Is there a way to do this automatically, perhaps even using third party tools such as resharper (which is C# only I think?) or similar? I get a headache even thinking about the work I need to do to make this change manually[code]....
I am struggling to get inheritance to work in the way that I understand it is supposed to work.I want to create a base class that uses MustInherit. It will have properties. The derived class should have access to those properties. But how do I get and set property values for an instance of the derived class?
So I have Public MustInherit Class Baseperson
Private _Name Public Property Name as string
[Code]...
But this does not provide encapsulation of the property so it would not seem to be a good solution.
I see various documentation on MSDN that talks about "abstract" classes having properties but I don't see how to make it work.
What is the difference between a class with protected constructors and a class marked as MustInherit? (I'm programming in VB.Net but it probably equally applies to c#). The reason I ask is because I have an abstract class that I want to convert the constructors to shared/static methods. (To add some constraints). I can't do this because it's not possible to create an instance in the shared function.
I'm looking at a VB.NET class (that I didn't write) that is declared "MustInherit" (abstract in C#, I believe) that has three methods, all of which are defined as "shared" (static in C#). There are no properties or fields in the class - only the three methods. From an OO perspective, does this make any sense?
My thinking is no, because by making it MustInherit, you're essentially saying you can't create an instance of this class - you must inherit from it and create an instance of the derived class. But since all the methods are shared, you'll never actually create an instance of the parent class anyway, so the "MustInherit" does no good. You might as well not mark it MustInherit and just inherit from it whenever you want.
When attempting to create a UserControl type that must be inherited, when I try to edit one of its child classes in the Form Designer, I am not allowed to edit the child UserControl with the message:
To prevent possible data loss before loading the designer, the following errors must be resolved: 1 Error
The designer must create an instance of type "XX_ExpandContentsPanel2.IOCardMaster", but it cannot because the type is declared as abstract.
This error goes away if I remove the "MustInherit" restriction.Is there some way around this or do I just have to accept the (bonkers-mad) restriction, and not declare my class as as MustInherit, even though it's not a useful control in its own right?
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.
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
CREATE TABLE [LogLevel] ( [Id] int primary key ,[Name] nvarchar(50) not null
[code]....
After creating a fresh endity model, I add the two tables above. When I try to build I get the following errors...
Type argument 'Inxsol.CommandPlan.Data.Model.Log.LogLevel' does not satisfy the 'Class' constraint for type parameter 'TEntity'. Value of type 'System.Data.Objects.DataClasses.EntityReference(Of Inxsol.CommandPlan.Data.Model.LogLevel)' cannot be converted to 'System.Data.Objects.DataClasses.EntityReference(Of Inxsol.CommandPlan.Data.Model.Log.LogLevel)'.
I have the following sample code in a VB.NET console application. It compiles and works, but feels like a hack. Is there a way to define EmptyChild so that it inherits from Intermediate(Of T As Class) without using the dummy EmptyClass?
Module Module1 Sub Main() Dim Child1 = New RealChild()[code].....
The other way to do this would be to move the generic code out of the Base class and then create 2 Intermediate classes like this [code]...
Then RealChild would inherit from the generic Intermediate and EmptyChild would inherit from the non-generic Intermediate. My problem with that solution is that the Base class is in a separate assembly and I need to keep the code that handles the generic type in that assembly. And there is functionality in the Intermediate class that does not belong in the assembly with the Base class.
I'm a newbie to VB, and I am having difficulty understanding what the following (legacy code) class declaration actually means: Public MustInherit Class ModelBase(Of T As {ModelBase(Of T, TIdType), New}, TIdType)
There is also a related ModelBaseCollection: Public MustInherit Class ModelBaseCollection(Of TCollection As {ModelBaseCollection(Of TCollection, TModel, TIdType), New}, TModel As {ModelBase(Of TModel, TIdType), New}, TIdType) Inherits Collection(Of TModel)
I have difficulty understanding the need for the ModelBaseCollection class as the ModelBase class is a generic type.
Consider a MyForm class that contains a shadowed implementation of Show(). It also contains a CreateForm() method, which accepts an instance of the form and calls the shadowed sub:
I have a bunch of classes that all contain a Shared ReadOnly Dictionary. If I want to access that Dictionary when the class is a generic type (such as when I have a wrapper function that takes T as an interface that all of these classes implement), what's the way to do it?
I want to do something like GetType(T).GetMember("Dict"), but that will return a MemberInfo type, and that cannot be cast to a Dictionary of my defined type(s). For calling functions this way, one can use a delegate + CreateDelegate + GetMethod. But there doesn't seem to be an equivalent Create*for GetMember stuff. Or am I missing something?
If I plug the GetMember call into the immediate window, and then use a subscript as if it is an array, then the debug output says I am getting a Dictionary back. But if I use that same approach in the actual function that I am trying to write, then I get an error about System.Reflection.MemberInfo cannot be converted to Dictionary(X, Y)
Suppose I want to write a generic function that will return the fully qualified name of the data type. In other words, how would you implement the following: Public Shared Function Foo(Of T)() As String ' Return the fully qualified name of T End Function
I'm tyring to pass a variable data type to a template class. Something like this:
frmExample = New LookupForm(Of Models.MyClass) 'Works fine
Dim SelectedType As Type = InstanceOfMyClass.GetType() 'Works fine frmExample = New LookupForm(Of SelectedType) 'Ba-bow! frmExample = New LookupForm(Of InstanceOfMyClass.GetType()) 'Ba-bow!
[Code].....
I'm assuming it's something to do with the template being processed at compile time but even if I'm off the mark there, it wouldn't solve my problem anyway. I can't find any relevant information on using Reflection to instance template classes either.
(How) can I create an instance of a dynamically typed repository at runtime?
I want to receive command line argument in my application like this.I have two different projects A and b when i execute A it should give an error message ( No Arguments ) but if i executes the project B ( it should pass a command line argument and the project A should start normally. the problem it that i can start application with arguments but i do not know how to receive arguments and execute different processes.
I'm using a web service programmed in Visual Basic .NET 3.5 to receive a JSON Array sent from other application.
I'm sending a JSON string like this one: [{"idRecoleccion":1,"PIN":"553648138"},{"idRecoleccion":2,"PIN":"553648138"}] And I'm receiving the code in Visual Basic .NET as follows:
I have some existing code to create an Excel spreadsheet and it works OK. I wanted to modify it to do some conditional formatting. But I get the messages xlCellValue, xlEqual, Formula are not declared and named argument expected. I have no references for Office or Excel.
Public myExcel As Object myExcel = CreateObject("Excel.application") myExcel.cells("C2:DG61").select() myExcel.selection.formatconditions.delete() myExcel.selection.formatconditions.add (Type:=xlCellValue,Operator:=xlEqual,Formula 1:="1") myExcel.selection.formatconditions(1).interior.colourindex = 48
I am using VB.Net. I have an object class called clsA(of T as clsB). Depending on what T is, I want to do different things. Let's say that clsC and clsD both inherit clsB and therefore can be used for T.
If I have an instance of clsA(of clsC), how can I get the inside type (i.e. clsC) using reflection?
Public 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?
I am trying to construct a generic interface class with generic functions. My goal was to use this to implement multiple worker classes for database interaction that have the same basic functionality. Each class will deal with different object for example, category, product or supplier but unless the the functions in the interface are generic that this won't work.This is the interface code that I have but I don't know if I have done it correctly. [code]
I am trying to create a list of a generic type in vb.net 2.0 framework. This is the generic type definition:
Public Class GenericParamMap(Of T) Public Sub New(ByVal pParamName As String, ByVal pPropValue As T) mParamName = pParamName
[Code]....
The compiler does not allow a "T" in the method's parameter because it's not defined, but I'm not sure how or where to define it. I thought it was okay to have a generic method definition.
I am trying to write a generic method, to avoid code duplication, which will create or activate a Form as an MDI children, based on its type. But I have to lines in error (see comments).
I've spent quite a bit of time reading up on generics, covariance, etc., and I am failing to understand why I get the aforementioned compiler error in this type of codeLet's say I have a base "Bill" class made up of a collection of Lines..
Public Class Bill(Of L As Line) Private _lines As List(Of L) Public Property Lines() As List(Of L)
I have the below lines of code :I am getting the error as mentioned in the Title above.This error has come after converting a C# Code to VB.NET Code which is mentioned below:
C#: public override IChannelListener<TChannel> BuildChannelListener<TChannel>(BindingContext context) { if (context == null)
