.net - Override Variables Declared In A Class?
Dec 16, 2010
I'm trying to create a generic Controller Class for generic events. But these these events still need to access their class variable. So my idea is to create the Base Controller Class with a ModelBaseclass variable as _ClassVar, which is inherited by all of the other class Controller classes will derive from. But I want the derived controller classes to override the _ClassVar with whichever one they need.
I want to do this, so the ControllerBaseClass can have all the generic functions that all the Derived Classes would use.
Model :
Public Class ModelBaseClass
Public Overridable Function Foo() As String
Return "Name"
[Code].....
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Jul 29, 2010
how variables declared with protected access in a base class are used to implement inheritance.
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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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Aug 20, 2010
I have a simple table in an access database that I'm using in a VS2010 project. I have a combobox control that a user can select the horse power of a motor. I then take that selected value from the control and copy it to a string variable called gstrSelectedHP. All I want to do is run a query that will pull up the full load amps of that horse power motor from the table. I have the query already, but I need to somehow put the gstrSelectedHP in the WHERE part of the query so that it only returns that value.
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Dec 8, 2009
Recently started swicthing our project from 1.1 to 2.0 framework:
getting lot of errors:
Saying VBNullString is not declared
If ScanString <> vbNullString Then
Stored = ScanString
End If
[Code]....
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Jul 15, 2011
I have a list of variables that are being created on one line.
Dim strFirstname, strMiddleName, strLastName As String
Is it possible to set the values for all of them at once? I know this doesn't work, but this is what I'm trying to do :
Dim strFirstname, strMiddleName, strLastName As String = ""
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Apr 23, 2009
I have the following code and i do no know why the program tells me that the variables are not declared.
[Code]...
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Sep 4, 2011
I have declared 2 variables as Double in my VB Code. Example:[code]Somerwhere down the code, after some internal calculations, the variables A1 and B1 have attained new values. Example:[code]Do I need to do a conversion of some sort in my program codes ??
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Sep 30, 2009
I am trying to bind a few values in xaml to variables declared in the code behind.
e.g.
vb.net
dim test as integer = 2
[code]....
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Mar 23, 2012
I define some global variables of a class as follows:
Private Class MyClass
Private var1 as Decimal
Private list1 as List(Of string)[code].....
But I found that after this form is closed, all above variables, var1, list1, list2 still exist in memory. I thought they should be collected by gc since the form is already disposed as I confirmed.
Add: I have monitored half an hour after the form is closed. But these variables are not collected by gc. I have an automatic update procedure on the form which uses above variables.Since the above variables still hold values, the automatic update procedure is always called which causes exception. (One quick fix is to check if form.isDisposed in update procedure. But I do not think this is elegeant. Besides, these variables occupy memory.)
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Jan 12, 2010
I have a listview but I would like to add 3 properties (for example one of them is "image") to the listviewitems in it. I was fine with making a custom class with the 3 properties and just inheriting ListViewItem but now I need to use MultiSelect, so it means doing things like(in For Each loops):
ListView1.SelectedItems.Item(i).Image don't work because it returns a ListViewItem not my CustomClass. I could always do : Ctype(ListView1.selectedItems(i), MyCustomClass).Image
But using that over and over again seems like a waste/wrong way to do it?
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Jun 9, 2012
I'm new in .NET programming.I have a class Form1 that includes Button1_Click event.Button1_Click creates a multiple Text Boxies at run time)Here is the class:
Public Class Form1
Dim shiftDown As Integer
Dim counter As Integer
[code].....
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Nov 9, 2011
When editing vb.net forms code in vs2008, how do I select base class events that I want to override? In vs2003 there was a list of overridables in the drop down list but now that list is missing?
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Mar 31, 2011
I have a base class, with a const giving its name. If I inherit that class, how can I override the const to give the name of the new class?E.g. (and I know this won't compile!)
Public MustInherit Class BaseClass
Const ClassName="BaseClass"
Public Sub DisplayName
MsgBox(ClassName)
[code]....
What I want is for class One to display its own name, not that of the base class.
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May 20, 2011
At the moment I have the following Command class:
Public Class SubscribeCommand
Implements ICommand
Private ReadOnly _vm As MainWindowViewModel
Public Sub New(ByVal vm As MainWindowViewModel)
_vm = vm
End Sub
[Code]...
In a tutorial i read, you have to implement add {} and remove {} for the canExecuteChanged-Event. But how can i do that, with vb.net?
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Oct 8, 2010
Can we override a Public Shared method in derived class? If not why?
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May 31, 2012
I am using Linq to Sql that generated a data contract for a table. I have a date field in that table which is a non-nullable field. I need to override the auto generated property of the date field to return a specific value, something like [code]Is it possible to override an autogenerated property in the designer.vb file using a partial class? I dont want to create a new property as it is currently being accessed in n number of places and I dont want to change it in every place.
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Sep 3, 2010
I wasn't ment to post anywhere, but I'm having a massive headacke.I've searched the Internet, tried many different way, but nothing to do.. I can't fix this, I don't even know why this is happening ..See the end of this message for details on invoking just-in-time (JIT) debugging instead of this dialog box.
************** Exception Text **************
System.InvalidOperationException: An error occurred creating the form. See Exception.InnerException for details. The error is: Class not registered (Exception from
[code]......
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Jul 26, 2010
I have a text file to read, at the first line will have a size of array, that means I cannot guess size of array, and I have to create a array in side a sub (Local Variable). Then, I want to use value of array in another sub, but I cannot use value of variable of another sub. What I have to do to make an array con be used in every sub/function in a class? Also, I've post an example file, code and error list.
[Code]...
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May 9, 2009
Public WithEvents Tree as Tree. I am not able to Serialize the Tree class, but if i remove the "WithEvents" keyword, it works fine. Why? What should I do if I have to declare it with "WithEvents"?
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May 4, 2012
I want to see if there is a way to do this... I'm Using vs2010 with the WP7 SDK. (VB.NET)
I am declaring this in the global scope.
public objGame as object then say i have classes: Game1 and Game2 for the sake of the example we'll just say both classes have an Update() function
I want to set objGame = Game1 (or Game2) and then be able to call objGame.Update()
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Nov 4, 2010
I have a VB .net application which works fine on a 32 bit systems. We tried using it on a 64bit Windows 7 system but it failed. So I set up an environment in a VM (windows 7 64bit VS 2005 SP1 all updated) and started debugging there. The problem I come across is, I have a module (Public variables and function declarations from a driver provider FTDI). When a function from module is called the result is saved in a variable also from module. But the problem is the variable is not declared.
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Aug 24, 2009
I am looking for a good resource on variable naming conventions to illustrate variable type and where variables are declared. So I will have public variables, Private variables, private or local variables. I also may want to declare variables with the same name in different class code (i.e. in the code behind different forms). I am assuming good coding would dicatate a prefix for declaration location.
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Nov 5, 2009
I want to be able have the class autofire a function when it is first declared. In my example it would be to load from a file all the constant variables for use in the program.
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Oct 13, 2009
I am try to learn to use Mysql / MySql.Data.MySqlClientI did find sample how to connect to Mysql but I want to have it in Class or Module so I only call open database when I open the form
How can I fix this Name 'connStr' is not declared
CODE:
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Sep 22, 2009
I have an object that I know was originally declared was an enum, but I need tothe specificnum type. I'm aware of the GetType method and it appears to work correctly, but I can't figure out how to go from there to a direct type comparison For reference types, you can use Typeof(object1) Is Class1, but this doesn't seem to work for value types.
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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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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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Jun 4, 2010
I 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...
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Oct 18, 2011
I have some variables in my main Form, but I want them in all my other forms, how can I make them kinda global or something?
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