What is the difference between these two methods for defining property value defaults? [code] Is there a reason to use one method over the other for defining the default property values in a class?
View 24 Replies
I create a class "Planet" that can be inherited. One of the purposes of inheriting is to create a template with different default property values. Eg:
Public Sub New
MyBase.New
MyBase.ForeColor = Red
[code]....
Now, to stop the defaults serializing in the InitializeComponent method, there are 2 ways:If I've implemented the properties using the 'DefaultValue' attribute, and made them overridable, the attribute can be overriden with the new value.The problem with this is, there's no way to just make just the attributes overridable, as opposed to the whole property.I could implement every property with protected Reset'PropertyName' and ShouldSerialize'PropertyName' methods. However, this is a bit of a pain in the arse.Is it, generally, an important consideration to ensure that someone who overrides your base class has the ability to change the default values of a property?
I have in my database a table for Products with one field as Price. For each invoice i want to be able to change this default price, so in my table for Invoice Details I have made another field called Price1. When I am entering invoice details and i enter a product number i want my program to select the relevent default 'Price' and insert it into 'Price1' so that it will be editable and so it can be saved to my database.
View 2 RepliesI believe that the correct way to give a property a default value is to use the Default Attribute on the Property.[code]In the property window, the value that's displayed in a grid's property bag when it's newly dropped onto a form is False, not True. It does recognise that the default value should be True because it shows the value as bolded and then de-bolds it when we manualy set it to true - but it doesn't respect the default as the initial value. Is there any way of getting the property bag to respect the default value?
View 4 RepliesFor a given class, with a default property of list, you can access an instance object in the list by doing myClass.defProperty("key"). You can also achieve the same results by typing myClass.defProperty!Key.
I have been told that using the parenthesis and quotes is faster for the way the runtime accesses the Property, but I'd like to understand what is the difference and how do each work...
I understand C# has a similar behavior by replacing the parenthesis with square brackets.
Is there anyway to have a class that can return a default type without specifying the property.
If I had a class that had a few properties and one property returned a string value and others returned additional types, could I do the following?
Dim StudentGrade as new StudentGradeClass
'call and get default property
Dim CurrentGrade as string=StudentGrade
'instead of this
Dim CurrentGrade as string=StudentGrade.Current
The reason I am asking this is when I have classes that have other classes as properties and would like to just get a default return value,.
I'm attempting the following:Default Public Property Data(Of dataType)(ByVal key As String) As dataType
Get
Return DirectCast(values.Item(key), dataType)
End Get
Set(ByVal value As dataType)
values.Item(key) = value
End Set
End Property
[Code]...
It made more sense to make it a property, and it would be the default property of the class. The data type can not be specified on instantiation of the class, because it can contain multiple objects of different data types.
I'm attempting the following:
Default Public Property Data(Of dataType)(ByVal key As String) As dataType
Get
Return DirectCast(values.Item(key), dataType)
[code].....
I have a FontFamily property, but I don't know how set the default value:
Public UnitsFontFamilyProperty As DependencyProperty = DependencyProperty.Register("UnitsFontFamily", GetType(FontFamily), GetType(ValueAndUnit), New FrameworkPropertyMetadata(New
[Code]....
I'm converting Visual Basic.Net code to C# in my project. But I have some doubts on how to convert Visual Basic default property to C#. The first option that comes to me are the indexers. Lets imagine the next code in Visual Basic
Public Class MyClass
Dim MyHash as Hashtable
Public sub New()
[Code]....
The following XAML produces an AmbiguousMatchException. The DataContext for myText is a DataTable consisting of > 1 row which contains a DataColumn named "test":
<TextBox Name="myText" Text="{Binding Path=Rows[0].Item[test]}"/>
When I modify the binding path syntax to the below example, the binding works as expected:
<TextBox Name="myText" Text="{Binding Path=Rows[0][test]}"/>
Given that the name of the DataTable is "myData", both of the following lines of code reference the contents of the column "test" on row 0:
myData.Rows(0)("test")
myData.Rows(0).Item("test")
Why doesn't the syntax that explicitly names the Item property appear to work in a binding scenario?
I am inheriting my own DataGridView (say MyDataGridView) from the standard DataGridView control. What I want is that certain properties of MyDataGridView should have a different default value than what its base have. For example, AllowUserToAddRows, AllowUserToDeleteRows, AllowUserToResizeRows properties should have the default values of False; so that when I drag MyDataGridView into a form in the IDE, the default values shown in the properties grid should be False. Later on, if I want to change them to True from the grid, they will be set accordingly.
View 1 RepliesI am new to classes, and I am new to Visual Basic in general, but I am working on a multi class program. The code seems to be correct, but I am trying on instantiate a class oject with the code:
View 3 RepliesI am making a new class that requires a lot of input information. Some of the properties need to be set to a default value, however I do not want to hard code them into the class.
What do you think would be the most efficient way to populate these properties?
I've been thinking of making a new class to hold all the default props and pass them as one object into the new class as a single argument but it seems kind of clunky.
Given a simple class like this:
Public Class clsOB
Implements System.ComponentModel.INotifyPropertyChanged
Private _Frequency As Double
Private _Value As Double
Public Event PropertyChanged(ByVal sender As Object, ByVal e As
[Code] .....
And then I'd like to do something like this:
Dim
o As
New
clsOB(50, 30)
o = 31
I am getting a strange error when I try to build my solution. The error occurs when I am calling the oGetHeaderValue function and passing the parameters.
Dim oGetHeaderValue As New clsGetHeaderValue
Dim returnString As String
returnString = oGetHeaderValue(strInvoiceNumber, strOrderNumber)
The error message is: Class 'clsGetHeaderValue' cannot be indexed because it has no default property.
I use the following line of code within a single method to explicitly check and trust an SSL cert from the following host: MyTrustedCompany.com:
ServicePointManager.ServerCertificateValidationCallback = Function(obj As [Object], certificate As X509Certificate, chain As X509Chain, errors As SslPolicyErrors) (certificate.Subject.Contains("CN=MyTrustedCompany.com"))
No problem with the code -> works perfectly 100%.
The problem is, it is too far reaching. I thought its scope would only be within the method I decalred it, but apparently it is a Shared property on the 'ServicePointManager' object, and must then persist for the entire application, which I do not want.
The problem is later I am calling web services of mine, etc and getting the "Could not establish a trust relationship..." exception. This is because in the line of code above I check for the host name of an SSL cert specefic to that method. I quickly tested Returning 'True' from the callback so all certs would be trusted instead of checking for a specefic name (i.e. MyTrustedCompany) and subsiquent requests worked. This is how I know this callback assignment reaches father than that single method. Sure I could extend the callback to include all other certitificate names, but what I would rather do is set the 'ServerCertificateValidationCallback' back to its default behavior. Like the pseudo code below:
ServicePointManager.ServerCertificateValidationCallback = Nothing 'Default checking behavior
How do I remove the custom validation and set it back to its default behavior?
I am inheriting my own datagridview (say MyDataGridView) from the standard datagridview control. What I want is that certain properties of MyDataGridView should have a different default value than what its base have. For example, AllowUserToAddRows,
[Code]...
Option Strict Off
Option Explicit On
Module ModGlobal
[Code].....
End ModuleI am getting this warning s when i upgrade from VB 6 to VB.NET .,I am verz new to this Visual Basic .
I need to set the default property of a dotNet Control used by an VB6 Application.
<ComClass(myControl.ClassId, myControl.InterfaceId, myControl.EventsId)> _
<DefaultProperty("NewProperty")> _
Public Class myControl
[code]....
I am newer in VB NET.
VB code:
Public Class InputBox
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim a, b, S, p
a = InputBox("Enter length")
b = InputBox("Enter width")
S = a * b
p = a + a + b + b
End Sub
End Class
In InputBox lines i get this error:
Class 'LearningVB.InputBox' cannot be indexed because it has no default property.
The BackColor of the forms in Visual Studio are a light grey, called Control in the Properties panel. How would I set the BackColor property of a Label to this default color?
View 4 RepliesI am creating a customised version of the ListView control and there are several of the properties that a ListView has that I would like to be set to a different value to the ListView default when a user goes to use my user control.
From what I've found there seems to be a number of people suggesting just set them in the constructor, but to the best of my knowledge that would just mean that the user would not be able to change the properties in the PropertyGrid in the VS IDE.I assume this is probably something extremely simple that I have overlooked.
Am getting: "Structure cannot be indexed because it has no default property". What am I doing wrong?
With grid.Rows(10).Cells
Dim note As New Note With {.ID = "Blah", _
.Date = "1/1/2011", _
.Message = "AAA", _
[code]....
I have been trying to create a custom control based on the ListBox called FileListBox. I followed Microsoft's walkthrough but am having some trouble.
What I want is to add another property to the ListBox called SafeItems which is an ObjectCollection of strings (like the Items property). I will use the Items property to store a collection of Filenames as strings and I would like to store the corresponding SafeFilenames in the SafeItems collection.
This is what I've tried:
FileListBox.Designer.vb
<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Partial Class FileListBox
Inherits System.Windows.Forms.ListBox
[Code].....
[code]This is my Code the error is Class 'System.data.datatable' cannot be indexed because it has no default property.. When i try this code in oledb it works but here it wont..
View 1 RepliesI created a Custom Class and Implemented a Type Converter for it. I used this Custom Class as a new property of a Custom Control.Everything is fine at design time. I can set the values of this property but at run-time the values i entered resets back to the initial declaration i made.
View 5 RepliesWhile modifying my form, I was suddenly unable to place any of the controls onto the page - i kept getting an error:
"Components cannot be added in localization mode. Select Default in the Language property."
So I set my language to Default...thinking that perhaps it had somehow gotten set to another setting. That seemed to fix it...I could now add controls to the form. Suddenly however, when I run the form, I notice that my new changes aren't there. If I re-set the language property to what it was before setting it to default, I see the form I see when i run it...it's like there's 2 forms.
In VB6, you can set the Default property of a command button to True / False, and when you push the enter key, it will click the button for you.
What property is this in VBNet / C#?
Argument not specified for parameter 'index' of 'public readonly default property chars(index as integer)as char'. Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
[Code]...
