Shadows vs. Overrides in VB.Net.What's the difference between shadowing a function in a base class in a subclass and overriding the same function? There is performance issues involved too?I know how to shadow and how to override in VB.net. My question is about when and why should I shadow a function instead override it and vice-versa.
View 2 RepliesHi. what is the difference of sleep function and pause function (using timer) between a loop.
View 12 RepliesAs an OSS library author, I've always tried to make my stuff CLS compliant. But MS doesn't make this easy. They often put you in catch-22 situations, such as the following:You cannot have a protected variable differing only in case from the public property.You cannot have protected or public variables starting in an underscore or 'm_'. If you want to make a class really extensible, you often need to have protected variables matching public properties. Your least ugly exit is to add a suffix to the variable, like "Var" or "Value". That's nasty and unacceptable to me. I like clean code.I know of no .NET languages that don't support variables starting in an underscore, and I've used them in many places where the variable needs to be visible to subclasses.
I'm tired of the warnings, and I'm planning on turning off CLS compliance at the assembly level on my 30+ C# libraries.Are there any actual problems with turning off CLS compliance on libraries? Any real problems with doing this? Microsoft has issued unheedable guidance on software for decades, with less that 5% of it being worth the bytes it was encoded in. I can't find any evidence that this best practice has any real effect on anything. But, to be careful, I'm checking. And no, this is not a duplicate of the inverse of this question: Any reason not to mark a DLL as CLSCompliant?I'm looking for actual results and effects here, not the advice of a MS intern. For example, if IronPython, IronRuby, or F# are unable to read or write a variable starting with an underscore, that's an effect, although it would only cause a problem for users subclassing certain objects. If a language or tool is completely unable to use an assembly unless it is marked CLS compliant, now that's a big deal.
It seems that in the following example, TestProperty() and TestDouble() are functionally equivalent. Is the case? I usually use Property/Get when I have a single line "Return Variable_" type of "function", and Function when I have a more involved thing going on. Is that reasonable?
vb
Public Class TestClass
Public ReadOnly Property TestProperty() As Double
[code].....
I am coming from the C# world to VB.NET and this puzzles me. Why are there 2 ways of doing the same thing? or is there some difference I am not aware of? What is the difference between the following:
Public ReadOnly Property Test(ByVal v as String) As Integer
Get
Return SomeOperationOn(v)
End Get
End Property
And
Public Function Test(ByVal v as String) As Integer
Return SomeOperationOn(v)
End Function
When do you use one as opposed to the other?
What is the difference between Private Sub /private Function / Private Class and to use them?
View 4 RepliesI am taken DateTimePicker2, DateTimePicker3 n textbox6.Now i wanted to display the result of subtraction of these two dates(DateTimePicker2-DateTime Picker3) in textbox6 automatically. I don't want to enter the result manually. Plz hlp me I need it badly. I hav already tried in lost focus event also its nt workin.
View 6 RepliesOne of the problems with datediff function is that even if the two dates are 31-12-2011 and 01-01-2012,it will show the difference as 1 year.How to overcome this problem?
View 17 RepliesWhat's the difference between these two declarations for PInvoking a user32.dll function?The first way, which I've commented out since it gets an error (Type DllImport is not defined"), the second way works. [code]
View 5 RepliesJust curious on what the difference is between the "Me.Close" and the "End" code for Visual Basic in terms of writing a Exit Button?
View 13 RepliesIn VB.NET there is a keyword 'shadows'. Let's say I have a base class called 'Jedi' and a derived class called 'Yoda' which inherits from 'Jedi'. If I declare a method in 'Jedi' called 'ForcePush' and shadow that out in 'Yoda' then when calling the method on an instance of the 'Yoda' class, it will ignore the base class implementation and use the derived class' implementation. However if I have an instance of 'Yoda' that was declared originally as of type 'Jedi', i.e. Dim j as Jedi = new Yoda(), and called the 'ForcePush' method on the instance, it will use the Jedi implementation.
Now let's say I have an event that is called 'UsingForce' which is raised when the 'ForcePush' method is called, and I shadow the event out in the derived class (this is because 'Yoda' has an interface 'IForcePowers' that declares this event) and each class raises it's respective event.
If I have an instance of 'Yoda' that is declared as type 'Jedi' (like above) and I put an event handler on the 'UsingForce' event of 'Jedi', and then the 'ForcePush' method is called in the 'Yoda' class, will this event handler be reached?
I have a two windows forms classes, a base class and a derived class. The base class has an event handler which handles ValueChanged on some component. I have also written a different event handler for the same event on the derived class.
When I create an instance of the derived class and fire the event, I find that both event handlers run (the base class one and then the derived class one). But I want only the handler in the derived class to run.
Edit: Here is what the code looks like (can't post the actual code):
Public Class BaseForm
Inherits System.Windows.Forms.UserControl
(Windows Form Designer Generated Code)
[Code].....
It works, but doesn't save what I've changed it to. In the designer everything works fine. I can change the text and have it update on my button control. BUT once I run or rebuild in any way, the text property changes back to it's default value, in my case "Button Control"These are what I've tried, and I've tried all with both Shadows and Overrides - both with identical outcomes. So I've just indicated that with Shadows/Overrides.
vbnet
<DefaultValue("Button Control"), Browsable(True)> _ Public Shadows/Overrides Property Text As String Get Return MyBase.Text End Get Set(ByVal value As String) MyBase.Text = value Me.Invalidate() End Set End Property Private _Text As String = "Button Control" <DefaultValue("Button
[code]....
shadowing and delegate method?
View 8 RepliesWhen I find examples online of VB.NET watch some functions use:
(Protected / Partial) & (Friend / Shared) & (Sub / Function) exp()
End (Sub / Function)
what is the difference?
explain me the difference between them? I'm new to visual basic, and I need to know the very basic things in Visual Basic allowing me to become a professional User
View 8 RepliesI have a couple of small classes to represent parts in a search filter. If the searched value equals NonValue the filter is supposed to do nothing. This is defined in a Base Class:
Private Class BaseFilter
Protected NonValue As Object
Protected sQueryStringBase As String = "AND {0} {1} {2} "[code]......
When I then create a StringFilter and check for allowed value:
Dim stf As New StringFilter()
stf.CheckNonValue(MyString)
I get a NullReferenceException (NonValue = Nothing) , when I expected the NonValue object to be String.Empty. Is this a bug in my code, or am I trying to achieve polymorphism in a wrong way?
I'm in a project where it's pretty much my first time doing all the architecture myself,and I'm running into a frustrating situation. My architecture for forms seems to be correct from a heuristic perspective, but I don't think its implementation is correct.
My architecture is thus:
Base Class: OrderForm
Child Classes: PurchaseOrder, Invoice, Credit
[code].....
I have created a new usercontrol. My usercontrol contains several other controls like labels, buttons and so on ...When I set the Font property of the usercontrol I want that font property value to propagate down to the child controls.
View 2 RepliesThe function for getting the difference in days between two days is giving me a wrong answer here.What could i be doing wrong??? DateDiff(DateInterval.Day, CDate("28/1/2011"), CDate("31/1/2011"))
View 1 RepliesIs there a way to translate this code in VB? Most of it is easy, but I can't figure out a way to override the event handler.
public class MTObservableCollection<T> : ObservableCollection<T>
{
public MTObservableCollection()
{
[code]....
Protected Overrides Sub Dispose(ByVal disposing As Boolean)
Try
If disposing = true And components IsNot Nothing Then
components.Dispose()
End If
Finally
MyBase.Dispose(disposing)
End Try
End Sub
Error: Protected Overrides Sub Dispose(disposing As Boolean)' has multiple definitions with identical signatures.How can I call this without raising an error ?
Some of my DataGridViewCells return the wrong value in their GetClipboardContent method. They are cells in a DataGridViewComboBoxColumn cells, so they use the displayed property, not the value property of the cell. I want it to return the value itself.An initial attempt was simply using
Protected Overrides Function GetClipboardContent(ByVal rowIndex As Integer, ByVal firstCell As Boolean, ByVal lastCell As Boolean, ByVal inFirstRow As Boolean, ByVal inLastRow As Boolean, ByVal format As String) As Object Return Value End Function in my DataGridViewComboBoxCell descendant but then I noted that this method is called more than one time per cell value, once for every data format DataGridView supports by standard, which are format="HTML", "Text", "UnicodeText" and "Csv". For csv, the base implementation appends a comma if it's not the last cell, for html it adds the correct tags depending on if it's the first/last row/cell in the table/table row, etc. I consider this format-specific, not cell-value specific.
So how could I replace the value that ends up in the clipboard without re-implementing all those format-specific aspects? That would result in quite some code for functionality that already exists in the base class, wouldn't it?
I have a theoretical class Name_Order, that has a string Name and a int Order. I need to indicate that two Name_Order's are different, if the pair NameOrder is different, that is, or name or order are different. Now, overriding Equals no problemo, but I have some "issues" with GetHashCode:
[Code]...
I have a main class that has a Sub procedure with no implementation. Any derived class should override and implement this procedure, so I used MustOverride in the base class.
Now, any time this procedure is called, I need to set a specific Boolean variable to True at the beginning of the procedure and set it to False at the end.
Is there a way to avoid writing these two lines of code in procedure implementation of every single derived class? Can I set this value to True in the base class, then run procedure in the derived class and then set the value back in the base class?
I am setting my viewmodel as datacontext in my xaml but I override it to my view to make few functions work however to achieve the visibility on some grids and I have a property in my VM can I override my datacontext back to my VM? If so how? I have a stackpanel that has datacontext overriden as my grid and within that stackpanel I need to change the datacontext for a button.
View 1 RepliesI inherited DataGridViewTextBoxCell because I need to add some custom property to it.
At run-time after creating the DataGridView instance and bind the data I do the following:
For k As Integer = 0 To grid.Columns.Count - 1
grid.Columns(k).AutoSizeMode = DataGridViewAutoSizeColumnMode.ColumnHeader
If k > 0 Then grid.Columns(k).CellTemplate = New CustomCell()
Next
[Code]....
the cell type is never of type CustomCell but it remains DataGridViewTextBoxCell.
Is it the best override for Equals (in VB.NET) for an object having an unique ID? [code]I took that example from the MSDN, but not entirely sure if from all points of view (including performance) is the better solution.[code]
View 2 RepliesI know how to handle overriding form closing with FormClosing event and MessageBox prompt by setting e.cancel to true but how can I override deactivation of the mdi child form?
View 3 RepliesI have a DataViewGrid that is populated with emp records sorted by a 'header' record listing the managers name. Currently, the user is a ble to select any row, even the manager row. I want to modify the program to prevent users from being able to select the manager record or 'header' record
View 9 Replies