I've ported a large VB6 to VB.NET project and while it will compile correctly, I've had to comment out most of the event handlers as to get around there being no array collection for winform objects and so putting the various objects that were in at the collection array into a List object.
For example, in VB6 you could have an array of Buttons. In my code I've got
Dim WithEvents cmdButtons As New List(Of Button)
(and in the Load event, the List is propagated)
Obviously, you can't fire an event on a container. Is there though a way to fire the events from the contents of the container (which will have different names)?
In the Button creation code, the event name is there, but from what I understand the handler won't intercept as the Handles part of the code is not there (commented out).
I'm not exactly sure what you're after, but if you want to be able to add event handlers to some buttons in a container and also have those buttons referenced in a List, you can do something like
Public Class Form1
Dim myButtons As List(Of Button)
Private Sub AddButtonsToList(targetContainer As Control)
myButtons = New List(Of Button)
For Each c In targetContainer.Controls
If TypeOf c Is Button Then
Dim bn = DirectCast(c, Button)
AddHandler bn.Click, AddressOf SomeButton_Click
myButtons.Add(bn)
End If
Next
End Sub
Private Sub SomeButton_Click(sender As Object, e As EventArgs)
Dim bn = DirectCast(sender, Button)
MsgBox("You clicked " & bn.Name)
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
' GroupBox1 has some Buttons in it
AddButtonsToList(GroupBox1)
End Sub
End Class
Related
i want to add a tabcontrol tab by pressing on a button:
Dim inp As String
inp = TextBox6.Text
TabControl2.TabPages.Add(inp)
and when i open this tabpage some object should be already created like a button and a textbox, etc.
i havent found any type of onload events for a tabpage so i tried to add this with:
TabPage8.Controls.Add(New Button())
tabpage8 would be the name of the new created tabpage but like vb already told me, i cant add objects to a tabpage which doesnt exist at that time.
is there any way i can do that or have you any other ideas which could help me?
Your code is close. Try the following:
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
TabControl2.TabPages.Add("Test")
Dim tp = TabControl2.TabPages(TabControl2.TabPages.Count - 1)
Dim b = New Button()
b.Text = "My Button"
tp.Controls.Add(b)
AddHandler b.Click, AddressOf MyButton_Click
End Sub
Private Sub MyButton_Click(sender As Object, e As EventArgs)
MessageBox.Show("MyButton clicked")
End Sub
This code grabs the last page added and adds a button to it. It also configures the button as needed and adds an event handler.
I have a form with many different radiobuttons, checkboxes and textboxes. Depending on their values I start my calculations. The results are shown on the same form and panel. If any of my controls (checkboxes, ...) changes, I want to immediatly update the results without a need to press any update-button.
I could define a statsChanged-sub for every single control on the form but there are so many. Isn't there a way/event of the form starting whenever a control is changed? It should be something like controlOnFormChanged. How can I get a sub that starts whenever a any control on the form changed?
Thank you in advance!
You could wire up the events that correspond to the desired change manually to a specific event handler:
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'Iterate through all controls and handle them according to their type
For Each c As Control In Me.Controls
If TypeOf (c) Is CheckBox Then
AddHandler CType(c, CheckBox).CheckedChanged, AddressOf SomethingChanged
ElseIf TypeOf (c) Is RadioButton Then
AddHandler CType(c, RadioButton).CheckedChanged, AddressOf SomethingChanged
ElseIf TypeOf (c) Is TextBox Then
AddHandler CType(c, TextBox).TextChanged, AddressOf SomethingChanged
ElseIf ......
......
End If
Next
End Sub
Private Sub SomethingChanged(sender As Object, e As EventArgs)
'Whatever it is you do
End Sub
End Class
Whenever one of the events on a control fires the sub SomethingChanged is called, allowing you to update your results.
Please be aware: If you have controls in subcontainers like Panels you need to modify this method and iteratively get all controls in all containers.
Here is, for example, a solution to this:
http://kon-phum.com/tutors/pascal/programming_cs_getcontrolsonform.html
Public Shared Function GetAllControls(ctrls As IList) As List(Of Control)
Dim RetCtrls As New List(Of Control)()
For Each ctl As Control In ctrls
RetCtrls.Add(ctl)
Dim SubCtrls As List(Of Control) = GetAllControls(ctl.Controls)
RetCtrls.AddRange(SubCtrls)
Next
Return RetCtrls
End Function
When using flash, I was able to get to the focus of an event by accessing the event's "target" attribute.
so if I remember, it was something similar to.
button1.addEventListener(mouse_click, doSomething);
doSomething(e: Event){
e.target.size = 50000;
}
And I'm looking for the equivalent in VB.
If you can give me it's common name across all languages, I'd be doubly grateful. I don't quite know what to search for aside from "event.target VB.net equivalent, and that's not returning anything.
Thanks in advance.
edit: for those new to flash. By focus, I mean the physical object that was clicked on. So the example given would be accessing the clicked button's size.
In VB you can wire up event handlers declaratively using the WithEvents keyword or imperatively using AddHandler.
Private WithEvents myButton
' OR
Public Sub New
Dim newButton = New Button()
AddHandler newButton.Click, AddressOf MyClickHandler
End New
'To consume it you declare a method as follows:
' The Handles clause is used when declaring WithEvents
Private Sub MyClickHandler(sender As Object, e As EventArgs) Handles myButton.Click
' The sender has a handle on the object that raised the event (aka the button)
Dim btn = DirectCast(sender, Button)
btn.Size = New Size(500, 500)
End Sub
Got it!
http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.button.onclick.aspx#Y0
Sub GreetingBtn_Click(ByVal sender As Object, ByVal e As EventArgs)
'When the button is clicked,
'change the button text, and disable it.
Dim clickedButton As Button = sender
clickedButton.Text = "...button clicked..."
clickedButton.Enabled = False
End Sub
The first parameter (sender by default) references the focused object. You can access it as you would any other normal variable, but it's information won't appear in the auto complete list unless you set it "As" that specific data type.
So I ended up with this
Private Sub nw_btn_Click(ByVal sender As System.Windows.Forms.Button, ByVal e AsSystem.EventArgs) Handles nw_btn.Click
sender.Hide()
End Sub
In VB6 there is a feature called Control Arrays, where you name controls the same name and provide them an index value. This allows you to set a value by looping through the controls and setting each value. In VB .NET I can't create a control array could someone provide me with a similar solution.
Here is a sample I wrote for something else that shows how to do something similar and shows how to do the handler as well. This makes a 10x10 grid of buttons that turn red when you click them.
Dim IsCreated(99) As Boolean
Dim Buttons As New Dictionary(Of String, Button)
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
For i As Integer = 0 To 99
Dim B As New Button
Me.Controls.Add(B)
B.Height = 30
B.Width = 40
B.Left = (i Mod 10) * 41
B.Top = (i \ 10) * 31
B.Text = Chr((i \ 10) + Asc("A")) & i Mod 10 + 1
Buttons.Add(B.Text, B)
B.Tag = i
AddHandler B.Click, AddressOf Button_Click
Next
End Sub
Private Sub Button_Click(ByVal sender As Object, ByVal e As System.EventArgs)
Dim B As Button = sender
IsCreated(B.Tag) = True
B.BackColor = Color.Red
End Sub
Avoid using the proposed iteration approaches, you'll get a fairly random collection of controls unless your form is very simple. Simply declare the control array in your code and initialize it in the form constructor. Like this:
Public Class Form1
Private OrderNumbers() As TextBox
Public Sub New()
InitializeComponent()
OrderNumbers = New TextBox() {TextBox1, TextBox2}
End Sub
End Class
You can now treat OrderNumbers just like you could in VB6.
Maybe this is simpler. To create a control array, I put the control array declaration in a module. For example, if I have a Form with three TextBoxes and I want the TextBoxes to be part of a control array called 'mytext', I declare my control array in a module as follows:
Module Module1
Public mytext() As TextBox = {Form1.TextBox1, Form1.TextBox2, Form1.TextBox3}
End Module
And, I use the TextBoxes from the control array as follows:
Public Class Form1
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
mytext(0).Text = "Hello"
mytext(1).Text = "Hi"
mytext(2).Text = "There"
End Sub
End Class
You can even loop through the control array, like you could in VB6:
Public Class Form1
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
For i As Integer = 0 To 2
mytext(i).Text = i + 1
Next
End Sub
End Class
The beauty of using a module is that the TextBoxes do not even need to be in the same form.
With Winforms, you could do this:
myForm.Controls _
.OfType(Of TextBox) _
.OrderBy(Function(c) c.Name) _
.Where(Function(c) c.Name.StartsWith("somePrefix")) _
.ToArray()
On your form you would name your textboxes somePrefix1, somePrefix2, etc.
Here is an old article but it could give you more information. The top method is super easy.
Your Form, or PanelControl, or anything else that can contain child controls will have a Property called Controls.
You can loop through all of the text boxes in a control by using
'Create a List of TextBoxes, like an Array but better
Dim myTextBoxControls As New List
For Each uxControl As UserControl in MyFormName.Controls
If TypeOf(uControl) is TextBox
myTextBoxControls.Add(uControl)
End IF
Next
Now you have your iterate-able collection you can work with.
You can access a TextBoxes value with the EditValue property.
After looking at what you're trying to do a little further.
You probably want to name all of your controls with a Prefix, let's say abc for now.
For Each uxControl As UserControl in MyFormName.Controls
If TypeOf(uControl) is TextBox Then
Dim tbControl As TextBox = DirectCast(uControl, TextBox)
If tbControl.Name.StartsWith("abc") Then
tbControl.EditValue = "the Value you want to initialize"
End If
End If
Next
So this is one of the features that did not make the transition to VB.NET -- exactly :-( However, you can accomplish much of what you would have done in VB6 with two different mechanisms in .NET: Looping through the controls collection and handling control events.
Looping Through the Controls Collection
In VB.NET every form and control container has a controls collection. This is a collection that you can loop through and then do an operation on the control like set the value.
Dim myTxt As TextBox
For Each ctl As Control In Me.Controls
If TypeOf ctl Is TextBox Then
myTxt = CType(ctl, TextBox)
myTxt.Text = "something"
End If
Next
In this code sample you iterate over the controls collection testing the type of the returned object. If you find a textbox, cast it to a textbox and then do something with it.
Handling Control Events
You can also handle events over multiple controls with one event handler like you would have using the control array in VB6. To do this you will use the Handles keyword.
Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged, TextBox2.TextChanged, TextBox3.TextChanged
Dim myTxt As TextBox = CType(sender, TextBox)
MessageBox.Show(myTxt.Text)
End Sub
The key here is the Handles keyword on the end of the event handler. You separate out the various controls that you want to handle and the event by using a comma. Make sure that you are handling controls that have the same event declaration. If you ever wondered what sender was for on every event well here's one of the uses for it. Cast the sender argument to the type of control that you are working with and assign it to a local variable. You will then be able to access and manipulate the control that fired the event just like you would have in VB6 if you specified and index to the array.
Using these two techniques you can replicate the functionality of control arrays in VB6. Good luck.
Private Sub Button3_Click(sender As System.Object, e As System.EventArgs) Handles Button3.Click
Dim a() As Control = GetControls("textbox")
For Each c As TextBox In a
c.Text = c.Name
Next
End Sub
Private Function GetControls(typeOfControl As String) As Control()
Dim allControls As New List(Of Control)
'this loop will get all the controls on the form
'no matter what the level of container nesting
'thanks to jmcilhinney at vbforums
Dim ctl As Control = Me.GetNextControl(Me, True)
Do Until ctl Is Nothing
allControls.Add(ctl)
ctl = Me.GetNextControl(ctl, True)
Loop
'now return the controls you want
Return allControls.OrderBy(Function(c) c.Name). _
Where( _
Function(c) (c.GetType.ToString.ToLower.Contains(typeOfControl.ToLower) AndAlso _
c.Name.Contains("Box")) _
).ToArray()
End Function
I'm using winform and fb.net.
Can someone provide me with an example of how to create a buttons click event?
I have
dim but as windows.forms.button
but.name
but.text
but.location
etc.
but I how do I create the Click and the code behind it?
You can use:
AddHandler button.Click, AddressOf HandlerMethod
In VB you can specify that a method handles a particular event for a particular control, if you're not creating it on the fly - you only need AddHandler when you're (say) dynamically populating a form with a set of buttons.
Here's a short but complete example:
Imports System.Windows.Forms
Public Class Test
<STAThread>
Public Shared Sub Main()
Dim f As New Form()
Dim b As New Button()
b.Text = "Click me!"
AddHandler b.Click, AddressOf ClickHandler
f.Controls.Add(b)
Application.Run(f)
End Sub
Private Shared Sub ClickHandler(sender As Object, e As EventArgs)
Dim b As Button = DirectCast(sender, Button)
b.Text = "Clicked"
End Sub
End Class
EDIT: To close the form, the simplest way is to get the form of the originating control:
Private Shared Sub ClickHandler(sender As Object, e As EventArgs)
Dim c As Control = DirectCast(sender, Control)
Dim f as Form = c.FindForm()
f.Close()
End Sub
In the winforms designer, add a button then double-click it. This will create the event (based on the button's name) and take you to the event's code.