So i am making a virtual os and im making a new user function.In the Login form i used a combobox for Selecting users and i'm stuck at creating a method to add the input for the new user to the combobox collection. this is what i have right now
Public Class NewUser
Private Sub FlatButton2_Click(sender As Object, e As EventArgs) Handles FlatButton2.Click
Form1.UserName(1) = FlatTextBox1.Text
Form1.FlatComboBox1.Items.Add = FlatTextBox1.Text
End Sub
End Class
i know its not much yet. but when i excecute this code it gives an error:Argument not specified for parameter 'item' of 'Public Function Add(item As Object) As Integer.
i really dont get how to fix this error.
Can someone help me please?
Add isn't a property, it's a method on ComboBox.ObjectCollection with one parameter, an Object. You need to invoke it like so
Form1.FlatComboBox1.Items.Add(FlatTextBox1.Text)
See the documentation for more info.
Related
I have a global method (in a module) that multiple forms are calling. I can't figure out how to pass/identify the calling form so that it's controls are recognised when referenced in the method:
Public Sub SomeFunction(callingForm As Form)
callingForm.ErrorProvider.SetError(TextBox1, "Faux pas!")
End Sub
Public Sub SomeOtherFunction(callingForm As Form)
SomeFunction(Me)
End Sub
I the above example, I've attempted passing the form as a parameter but I'm being told:
ErrorProvider is not a member of System.Windows.Forms.Form.
This is pretty common, to want to treat all your forms the same, yet different. You will want to create another class that each form can implement. This allows you to do something specific... generically.
Create a class similar to this, call it and the function whatever you want:
Public Interface IErrorForm
Sub MyValidate
End Interface
Implement it in your forms:
Public Class Form1
Implements IErrorForm
Public Sub MyValidate() Implements IErrorForm.MyValidate
'...Your code here
'TextBox1.Text = "Faux pas!"
End Sub
Now, wherever you want to call the function, you could do something like this:
Public Sub SomeFunction(callingForm As Form)
If GetType(IErrorForm).IsAssignableFrom(xFrm.GetType) Then
CType(xFrm, IErrorForm).MyValidate()
End If
End Sub
Another approach with returning value from Validate function
As you mentioned in the comments
...one of the key purposes of my method is to avoid having to set the
errors outside of the method, to reduce duplicitous code
As I understand you want Validate function check, given control as parameter, for errors and show error message through ErrorProvider.
My suggestion will be shared Validate function return string value, which contains error message generated after validating control
If no error then function return Nothing or String.Empty
Public Function Validate(ctrl As Object, formats As String) As String
Dim errorMessage As String = Nothing 'or String.Empty
' Your validating code here
' If no error errorMessage = Nothing
Return errorMessage
End Function
Then in the form (possible in the Validated event handler)
'....
Me.MyErrorprovider.SetError(Me.MyTextBox,
MyGlobalFunctions.Validate(Me.MyTextBox, "formats"))
I'm used to programming in C# so I have no idea how to approach delegates and passing methods in VB
The error that I am getting is: Argument not specified for parameter 'message' of 'Public Sub ReceiveMessage(message As String)'
Here is the constructor of the class that I am trying to pass to:
Delegate Sub ReceiveDelegate(message As String)
Public ReceiveMethod As ReceiveDelegate
Sub New(ByRef receive As ReceiveDelegate)
ReceiveMethod = receive
End Sub
This is the method that I am trying to pass to that constructor:
Public Sub ReceiveMessage(message As String)
MessageBox.Show(message)
End Sub
I'm using it as such:
Dim newClass As New Class(ReceiveMessage)
The purpose of this, is that once the class receives data from a network device, it can call the corresponding method on the Form asynchronously.
You need to create the delegate object and use the AddressOf operator, like this:
Dim newClass As New Class(New ReceiveDelegate(ReceiveMessage))
However, if you don't explicitly create the delegate object, VB.NET will automatically determine the right type, based on the signature, and create it for you, so you can just do it like this:
Dim newClass As New Class(AddressOf ReceiveMessage)
The latter is obviously less typing, but the former is more explicit. So, take your pick. Both ways are perfectly acceptable and common.
Ok, I am trying to pass data from one form to another form using the overload constructor method. I could just use public variables or properties, but would like to use the overload method.
Here is the code section from my first form that calls the second form...
Private Sub dgvAllWO_CellDoubleClick(sender As Object, e As System.Windows.Forms.DataGridViewCellEventArgs) Handles dgvAllWO.CellDoubleClick
Dim I As Integer
I = dgvAllWO.Rows(e.RowIndex).Cells.Item(0).Value
Dim frmWO(I) As New frmWorkOrder
End Sub
Here I have the code from the other form...
Public Class frmWorkOrder
Public Sub New(ByVal ID As Integer)
InitializeComponent()
End Sub
Public Sub New()
InitializeComponent()
End Sub
End Class
After doing that, i now get an error on 'NEW' on this line of code on my first form.
Dim frmWO(I) As New frmWorkOrder
Error 1 Arrays cannot be declared with 'New'
Why is this happening? After overloading the constructor my form class is turned into an array? Im not sure what is happening here. I am grateful for any help or direction you can give me. Thanks in advance.
In VB New is the constructor, so you need to pass the value to the constructor like this:
Dim frmWO As New frmWorkOrder(I)
If frmWO is an array, then something like this:
frmWO(I) = New frmWorkOrder(I)
This line:
Dim frmWO(I) As New frmWorkOrder
should be
Dim frmWO As New frmWorkOrder(I)
I have a little problem with an interface. A bunch of my classes implement the ILayoutObject interface. A method declares a variable as ILayoutObject (defaulting it as Nothing) and then runs some code which decides which object it should be. The problem is, the evaluation code runs in a method which receives the variable as a parameter and assigns an object to it. With objects, this would be no problem. The object would be affected by the changes in the method and everything would be OK. Howeverm, when using an interface, the variable in the calling code remains Nothing and behaves like a normal variable. Does anyone have any ideas on how to circumvent that? Alas, due to code structure I am unable to use ByRef or functions :(
Here is some code:
Protected LayoutHandler As Dictionary(Of String, Action(Of Constants.OptionsEntryStructure, ILayoutElements)) = New Dictionary(Of String, Action(Of Constants.OptionsEntryStructure, ILayoutElements)) From
{
{Constants.KeyLayoutType, AddressOf KeyLayoutType}
}
Sub MakeLayOuts
Dim LayoutElement As ILayoutElements = Nothing
Dim Value = "SomeValues"
Dim key = "Key"
LayoutHandler(key)(Value, LayoutElement)
' LayoutElement remains nothing.....
End Sub
Protected Sub KeyLayoutType(elem As Constants.OptionsEntryStructure, Layout As ILayoutElements)
Layout = New LayoutObject 'which would implement the interface
End Sub
You need to declare the parameter as ByRef if you want to alter the object to which the variable in the calling code points to:
Protected Sub KeyLayoutType(elem As Constants.OptionsEntryStructure, ByRef Layout As ILayoutElements)
Layout = New LayoutObject 'which would implement the interface
End Sub
This is true with any reference type (classes). The fact that they are referenced with an interface makes no difference.
If you can't use ByRef, and you can't use a function to return the new object, then your only other real option would be to request a type of object which has the layout object as a property. For instance:
Public Interface ILayoutElementContainer
Public Property LayoutElement As ILayoutElements
End Interface
Protected Sub KeyLayoutType(elem As Constants.OptionsEntryStructure, Container As ILayoutElementContainer)
Container.LayoutElement = New LayoutObject 'which would implement the interface
End Sub
I have been programming for some time, but I have some fundamental questions, one of them is as follows:
Public Class PriceListDetails
Dim pricelist As BSPLib.PriceLists.PriceList
Dim IsReadOnly1 As Boolean
Public Sub New(ByVal IsReadonly2 As Boolean)
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
'Readonly prevents from Modifying/Saving
IsReadOnly1 = IsReadonly
End Sub
End Class
Is it compulsory to create IsReadyOnly1 and IsReadyOnly2, is there a way to take the parameter from new method to IsReadyOnly1 Directly like in reference type?
Thank you.
Hard to tell what you mean, the posted code cannot compile. I'll suppose you mean this:
Private IsReadOnly As Boolean
Public Sub New(ByVal IsReadOnly As Boolean)
InitializeComponent()
Me.IsReadOnly = IsReadOnly
End Sub
Where the Me keyword ensures that the field is assigned instead of the parameter.
Setting members with constructor parameters is pretty much common practice in OOP. However, if you are using public properties then you could use object initializers as well:
Dim priceList1 = New PriceListDetails With {.IsReadOnly = True}
Boolean is not reference type variable, so it's not possible.
In case you want to copy the reference,then also you need both variable. You can take only IsReadonly2 as reference.