I 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.
I 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 RepliesGiven 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.
What i am having trouble doing is set the current parameter to the current row at a specific column like e.row[column index]
For Each trow As TableRow In table.Rows
cmd1.CommandText = "dbo.directway"
cmd1.CommandType = CommandType.StoredProcedure
cmd1.Connection = conn
[code]....
Class 'System.Web.UI.WebControls.TableRow' cannot be indexed because it has no default property.
If we say blue is the default colour of the Backcolor property I understand it as if you don't specify a colour for Backcolor blue will be its colour. But I could not make sense of default property of a class in the context of building a custom user control. After calling an instance of a class we have to either call one of its members or assign an other object for it. Therefore why should there be a default property?
View 9 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 RepliesBase class has one field to hold numeric balance value. With 2 methods that accept arguments for adding and subtracting the new input calculating new balance. Sub class has four fields dates, transaction, memo and amount.I have a deposit form, and withdraw form. Each time one transaction is entered it creates an object with sub class fields, then adds to the account collection. My problem is not understanding how to call the deposit/withdraw method and pass the current transaction amount back to the base class to alculate the new balance. Does anyone have any links to information/tutorials on how to perform something like this? As you can see with my code I have tried various different approaches without any success.
[Code]...
I'm sure there are several ways of achieving my goal but I am after opinions on what you think is the best option. I'm writing a vb.net application which (amongst other thinks) interfaces with media players in the home. Because there are different types of media playersI'm trying to structure it so each type of media player has it's own class which interfaces to a management class which sits on top of all the different devices types.
The device classes are responsible for discovering the phsyical devices and returning that information up to the management class. A device class may be responsible for monitoring 1 or more physical devices so..
[Code]...
I think this is a pretty basic question, but I just want to clarify. If I have a variable with a null value, and pass it as a parameter that is optional, will the parameter get the null value, or the default value?
dim str As String = "foo"
dim obj As Object
//call 1
[code].....
The date time picker control does not seem to be passing on its default value (which appears to be 'Now'), when bound to a datatable and then saved. I have to select 'today' or pick another time from the popup calendar for that date to be saved.
View 1 RepliesI'm using silverlight3 and vb.net..I want to pass the value from Default.aspx to my App or Main page. I wrote the code in my default.aspx page which it is returning the local ip address of the client System, I would like that same address to be used in my silverlight pages.
VB code
Dim clientIPAddress = System.Net.Dns
.GetHostAddresses(strHostName).GetValue(0).ToString()
This clientIPAddress will get the local ip of the client which is like 192.168.1.12. Now i want this value to be passed to my main page. How to pass this value from default.aspx to my main page.
I seem to have problem with passing a collection/sorted list/ list of strings from one class to another.I am using property procedure to pass it, however nothing is sent to another class. There isn't any error messages either.[code]
View 3 RepliesI have a very simple class that holds a few public properties - ID, Text, Colour, etc. and a Boolean called 'SelectedItem'. Just like the Checked property on RadioButtons, only one item can have its SelectedItem property set to True within a particular group. Note: there will be several separate groups (lists), each allowed to have only one item with SelectedItem = True.
My first thought was that I would probably just have to handle everything outside of the class, setting SelectedItem to False for every other item in a particular list when another item was selected. But that seems rather inelegant to me. So I've been trying to think of how this might be done within the class. For example: could I perhaps have a private string property called say "GroupName" - set in the New sub when adding a new instance of the class - and then use a private shared method to set every item's SelectedItem property to False, provided the item has the same GroupName as the newly selected item? I would have a go at doing this but I have no idea how to enumerate every instance of a class from within that class, or whether that's even possible. Is it? Or is there another (better) way to achieve my goal? Here is a cut-down version of what I've got so far:
Public Class ResourceItem
Public ID As Integer
Public Text As String[code]....
As can be seen: instead of instantiating a new ResourceItem and passing that as an argument to the manager's Add procedure, I'm simply passing the details of the new item and the procedure is creating the item from those. I don't know whether this is a good or bad idea - please advise - but I've done it because I couldn't figure out how to make the SelectedItem property only writeable by the manager, so I wanted to avoid having directly accessible objects that could have their SelectedItem property set to True without it deselecting all the other items in the same group. Of course that still leaves the possibility of setting a variable to one of the manager's list items and setting it from there, so I would still like to know how I could prevent that, if possible.
UPDATE: I didn't use the code above in the end, deciding instead to go with Cyborgx37's solution - which seems to work perfectly well for me despite the warnings about best practice. I also realised I would need to use the same class in another scenario where multiple items could be selected, so it was easy to add a Boolean property to the manager to enable that.
I am creating a procedure and would like to know if I can pass the name of a property. I.e ComboBox1 so I can change the properties of that object. What I have done is create a procedure to populate a Combobox from my MySQL database. What I want to do now is populate the relevant Comboboxes without having to create a new procedure specifically for each combobox. I can create a procedure for each Combobox but the whole reason for procedures and functions are to minimize repetitive code and to make code easier to manage.
At the moment my procedure is ProcedureName(ComboBox1, "DatabaseName", "DatabaseField").
What I want to be able to do is do
ProcedureName(ComboBox1, "DatabaseName", "DatabaseField1").
ProcedureName(ComboBox2, "DatabaseName", "DatabaseField2").
ProcedureName(ComboBox3, "DatabaseName", "DatabaseField3").
I have the following code:
Public Class MyColorsClass
'Constructors
Public Sub New()
'Empty Constructor
[code]....
However, if the empty constructor was called to instatiate this class then the colortype is not yet set. Therefore, if one accesses the 'IsColorCool' property it will always return 'False'. Now for the sake of this example, I must keep the empty constructor as part of the class.Now I could add some code in the 'IsPropertyCool' to check and see if a ColorType has been defined, and throw an exception if it has not been set, but I don't really want to do that.I also could always move the logic OUT of the property and into a method on the class called 'DefineIfColorIsCool' or something, and make the owness on the caller to make sure the method was called if they want to use the property 'IsColorCool'?
Supose a base class
Public Class airplane
Private var_num_seats As Integer
Private var_num_engines As Integer
[code]....
Obviously, I don't wish that the class Glider has the method "start_engines" neither the property "num_engines". Otherwise, other child classes may have. How can I supress these property and method in child class, not just ignoring (if I can)?
I have procedure (Import) that calls a for a new instance of frmImportData. I also have a class name clsBatch that has a data table property called prpParametersTable.For some reason, I get an error (indicated below with ERROR>>>) when trying to assign prpParameterTable to cv_dtImport2. The error states "Object reference not set to an instance of an object.". Why does this error not happen when I assign dtBP to cv_dtImport1? Both cv_dtImport1 and cv_dtImport2 are equal to Nothing and in my Import procedure dtBP = prpParametersTable.
Public Sub Import(ByVal clsB As clsBatch)
Try
Me.cv_clsB = clsB
[code]....
I have three class files, accounts.vb and transactions.vb in addition to my form.vb. I am unable to retrieve a member variable from on class from inside the other. When the combobox index changes, the program loads the correct account (checking or saving) from two different sequential files. I don't think I have the calcBalance procedure in the correct class file. And that is what I am having trouble with. Accessing it to display it. [Code]
View 1 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]....
[Code]....
I have attempted to invoke my vbscript in the webbrowser control using the invokescript function (im using wpf's webbrowser invokescript function but works the same mostly). I'm trying to pass multiple values but for some reason i cant. the problem code section is above and invokescript section is where it errors out.Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth. - "Sherlock holmes" "speak softly and carry a big stick" - theodore roosevelt. Fear leads to anger, anger leads to hate, hate leads to suffering - Yoda. Blog - [URL]
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].....
I'm looking for a tutorial on how to Adding a list(of Class) or Collection as another Class's Property.What I am after is something like the Columns Collection for the DatagridView control.I would like to add Items in the graphics screen. Where the item list is displayed in the left panel and the selected Item properties are displayed in the right panel.
View 4 RepliesI'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 Replies