.net - Why Can't Access The Backing Field On An Auto Implemented Property From Within An Inherited Class
Dec 20, 2011
I have a class that exposes an auto implemented property Enabled
[Code]...
But If I had not use an auto implemented property and declared my own backing-field as follows this is accessible from the subclass: Private _Enabled as Boolean ---- EDIT ----
The abve line is incorrect - this is not possible, it was in fact Protected in the original code which allowed access from the sub class See @JonSkeet answer ---- EDIT Of course I can just access Enabled from the sub class to work around this but can someone explain why this is the behaviour?
View 2 Replies
ADVERTISEMENT
Jul 10, 2009
I am wishing to emulate the auto code generation that happens when you derive from a class, such as Form, and declare the Public Sub New() constructor. When this happens the constructor will auto-generate code like the following:
Public Class MyInheritedForm
Inherits Form
Public Sub New()
[Code].....
View 3 Replies
Apr 1, 2012
[Code]...
Is there an explanation for this limitation? I mean, it's still in the constructor for the object, and the base class constructor is still executed first.
View 1 Replies
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]...
View 2 Replies
Oct 14, 2011
I have two classes[code]...
How can I modify class1 in a sub in class2?
View 2 Replies
Jun 11, 2009
I'm going to resolve this bug as "Postponed" as we won't have time to do it for VS2010, but I'm definitely interested in your feedback going forward.
View 6 Replies
Nov 30, 2010
I recently finished a class that we're using to tie Access to some WCF Services. Of course this means that the .Net classes (and all of their properties) need to be visible to COM. Given that I'm using VB10 and the Contact class has about 20 properties I went ahead and used auto-implementing properties.Much to my surprise, the properties were not accessible from within VBA in Access. I tried marking the properties as ComVisible (which I didn't have to do in the past with standard properties) and it still didn't work. After changing the auto properties to standard properties everything worked.
Became
Public Property FirstName As String
Get
[code].....
View 1 Replies
Feb 13, 2012
I have an 8 bit digital output board used for device controlling. Each external device needs one bit and is controlled by a different application.I have written a class library and the class DigitalOutputPort (VB 2010) that envelopes the driver that manages the 8 bit port. Each device application uses this class, creating its own instance.
In order to set a bit of the digital output port, I have to write a byte to that port: this byte is the bit mask for all 8 bits together: to set HIGH the bit number 0 - 1 - 2, I have to write 7 on the port, to set HIGH all 8 bits, I have to write 256, and so on...
All works fine when only ONE application uses the class. But if two applications want to set its own bit on that port, I get problems because I do not know the current value of all bits set by other applications (the driver has not such function) and, of course, I cannot change one bit without changing all the other (if I do not know the current bit mask)
Normally this looks like a typical case of sharing data between two application and my first idea was to write the current value of the port in a file on the disc, where all application can access and read it. But it seems to be too much heavy for this simple problem. Moreover it could also creates performance ans reliability problem.
Then I though about using a shared field (property) in the class. A shared field preserves its value between all instances of a class: but is it also true between instances from different applications? I cannot find more info about this last point, I have to make same test.
A third way would be that I create just only ONE instance of the class DigitalOutputPort, one for all applications.The first application that needs it, create the object, all other applications will used the already created object.I like more than other this way, but I do not know if and how it can be done.
View 1 Replies
Apr 29, 2011
I am working on an ASP.NET project where I use VB.NET within Visual Studio 2010. Some of the other developers on the project are using Visual Studio 2008. We all check our code into single SVN repository. I would like to start using Auto-Implemented Properties within VB.NET ...
Property FirstName as String
instead of ...
Private FirstName as String
[code].....
My concern is that this could mess up things for those using VS2008. What would happen if someone using VS2008 needed to modify my class that made use of Auto-Implemented Properties? I am assuming that since everything compiles down to IL code then there would be no issue in binary compatibility. Though a problem would arise when editing source.
View 1 Replies
Nov 10, 2011
I have somehow managed to disable auto-implemented properties in my VS2010 IDE how to turn it back on. Almost every article on the internet loves to explain auto-implemented properties but doesnt give you the crucial option of how to turn it on or off.
View 2 Replies
Jul 14, 2009
I am using Visual Studio 2005 (Visual Basic) and MS Access 2003 I am trying to build an application in the lines of the book "Doing Objects in Visual Basic 2005" by Deborah Kurata. So, I have a Data Access Layer (DAL) Class Library that is separated from the business logic layer (business objects) Class Library. I try to add a new business object such as a "Customer" to the Access Database, where the "Customer" table has a PrimaryKey "CustomerID" which is an AutoNumber field. I am successful in writing the values to the database, but I can't figure out how to know the "CustomerID" of a newly added "Customer" so I can populate the business object with the respective values.
View 4 Replies
Jun 28, 2011
I was simply wondering if in VB.Net there is a shorthand equivalent to this kind of C# including the private setter:
public string Test { get; private set; }
View 4 Replies
Mar 30, 2010
This is a bit of a continuation from a previous post for which AtmaWeapon was very informative.
Problem:
A parent class has a sub class with various properties. A property of the parent class is a List(of T) with T = the sub class The issue is how to store data in the sub class of the instantiated parent
Some example code (hopefully formatted correctly):
Code:
'=========== Class Definitions =============
Public Class courseClass
Public Class timeTableClass
[Code].....
View 7 Replies
Jul 7, 2009
I have made a front-end application in Visual Basic .NET that will store data entered by the user in a backend Access 2003 Database. The application has other functionality as well.If the user searchs for a previous record that has been stored in the Access Database, I query the Database (SELECT ... ) using an OLEDB Connection and then display the records on a Datagrid on my Form. Everything is working fine, however, the Column Headings of the Datagrid are the Field Names in my Database (FirstName, LastName,...) rather than Caption Values (First Name, Last Name,... )
I tried looking up the net, but most of the topics addressing a similar problems use DAO, and I understand that it is not completely supported in VB .NET. I am fairly new to VB .NET and I am not quite sure how to address the problem or where I am going wrong. I tried using FirstName.Caption but that gives a Runtime error (One or more parameters missing from the Sentence)
View 6 Replies
Nov 30, 2009
how ListView pointer is stored/removed at ReadOnly Property ListView in ListViewItem? How is it implemented? I know ListViewItems are stored in ListViewItemCollection which has constructor New(owner as ListView) but I dont know how pointer to ListView is add/remove in ReadOnly Property in ListViewItem...
View 1 Replies
Jun 3, 2010
Tabsize in a TextBox or RichTextBox. Anyone know why Microsoft have not implemented it as a PROPERTY?
View 1 Replies
Jul 6, 2010
Is it possible to populate an AutoComplete text box property in code from an Access query.
View 6 Replies
Feb 27, 2012
I have used ADOX for create some fields in my database in access but the required property of this appended fields (columns) are set in "yes" but I want to be them "No" who knows how can I solve this problem
View 3 Replies
Jan 2, 2012
I'm seeing a strange build bug a lot. Sometimes after typing some code we receive the following build error.
Class 'clsX' must implement 'Event PropertyChanged(sender As Object, e As PropertyChangedEventArgs)' for interface System.ComponentModel.INotifyPropertyChanged'.
And
'PropertyChanged' cannot implement 'PropertyChanged' because there is no matching event on interface 'System.ComponentModel.INotifyPropertyChanged'.
Those error should never go together! Usually we can just ignore the exception and build the solution but often enough this bug stops our build. (this happens a lot using Edit and Continue which is annoying)Removing the PropertyChanged event and retyping the same code! sometimes fixes this.We're using a code generator that causes this error to surface but just editing some files manually triggers this exception too. This error occur's on multiple machines using various setups.
View 4 Replies
Mar 30, 2010
VB.NET .NET 3.5 I have an aggregate class called Package as part of a shipping system. Package contains another class, BoxType . BoxType contains information about the box used to ship the package, such as length, width, etc. of the Box.
Package has a method called GetShippingRates. This method calls a separate helper class, ShipRater, and passes the Package itself as an argument. ShipRater examines the Package as well as the BoxType, and returns a list of possible shipping rates/methods.
What I would like to do is construct an Interface, IRateable, that would be supplied to the helper class ShipRater. So instead of:
[Code]...
However, ShipRater requires information from both the Package and its aggregate, BoxType. If I write an interface IRateable, then how can I use the BoxType properties to implement part of the Interface?
View 2 Replies
Dec 27, 2010
I have a base class which must be overriden. This base class sits in one dll shared by all. The derived classes will each be in their own dll such that the addition of a new derived class can be done by distributing a new dll. The set of dlls, and therefore the set of derived classes, will be discovered by the main program on startup. That's all pretty straightforward. The problem is that the main program needs to be able to query a database to figure out which type of derived class it needs, then create a class of that type. Naturally, it can't know which types will be available ahead of time because even I don't know that. The program has to be dynamically extensible.The obvious way to do this is to have an interface in the dll that is implemented by a class with a default constructor. The sole purpose of that class would be to return an object of the type (one of the derived types) defined in that dll. The derived types can't really be this class, because they can't have a default constructor since the base class doesn't have a default constructor, and the derived class can't make up the arguments that the base class constructor needs.
So basically, each dll that houses a derived class would also house a simple class that implemented an interface for the sole purpose of creating that particular derived class. The main program would examine the dll to find a class that implemented the interface, and once it found one, it could ask it what type of class it created, or it could ask it to create an instance of that class. It seems like there ought to be an easier way to dynamically add new classes to the project. It seems like the derived class ought to be able to tell the main project what type it was. This could be done, except that the derived class would have to exist before any of its methods could be called unless the methods were shared. Since you can't have a shared method in an interface, the interface itself would make no sense at that point, in which case I would need to discover whether the class in the dll derived from the base class in the second dll, just to figure out whether or not I wanted to create it. That's getting convoluted by now, so I guess I'll leave it there. The basic point is that the base class is known to the main program from a common dll. The number and types of derived classes can't be known at this time, so the program has to be able to discover them dynamically. Each derived class will sit in its own dll (or there could be more than one in a dll), and has to be discovered, and instances created, as needed, by the main program.
View 2 Replies
Jun 10, 2011
Suppose I have piece of code like this:
Public Interface ISomething
....
End Interface
[code]....
View 2 Replies
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?
View 2 Replies
Aug 27, 2011
Private _Order As Order() Public Property Order() As Order() Get Return _Order End Get Set(ByVal value As Order()) _Order = value End Set End Property
I need to get property name 'color' inside the 'order()' array, i am trying ' Order.color ' but its not getting,
View 4 Replies
Nov 16, 2010
I have a function that updates a Client in the database. A client object is passed in, along with a string array of fields/properties that should be updated. I need a way of accessing each property in the client object, based on what is in the array. Basically, I am looking for the VB .NET equivalent to this javascript:
var fields = ["Firstname","Lastname","DOB"];
for(field in fields)
{
[code]....
View 1 Replies
May 1, 2010
I know this is random but is there a way to specify that a property explicitly does not need to be inherited? So you can have two sub classes and one object will have that property and the other doesn't?
View 2 Replies
Nov 16, 2011
I frequently use TextBoxes that expect date values. I do a tedious job every time to handle the Validating event. The Validation event ensures that the value is a valid date value according to the current thread's Calendar, and if so, formats the date to "dd-MM-yyyy".
I want a TextBox (e.g. DateTextBox) that automatically runs validation and formats its Text property. All I have to do is dropping it to the form.
I know I should use inheritance; but I do not know where to put the auto-validation code; and I do not know how to save the inherited class as a control in the ToolBox.
View 4 Replies
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]...
View 7 Replies
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]...
View 2 Replies
Oct 31, 2010
On form1 I put a picturebox from the toolbox.[code]Is it possible to set picturebox.visible=true of the inherited picturebox?
View 1 Replies
