Newbie Questions

Question

Hi

I'm just starting with Visual basic. I found a funny MS guide called "Visual basic for Bright kids"

There I'm at the point of creating Click Event. Code bellow.

It's written as the guide tells to, but still I get two errors from MS Visual Basic 2005 Express.

1. Error 1 'Public Event Click(sender As Object, e As System.EventArgs)' is an event, and cannot be called directly. Use a 'RaiseEvent' statement to raise an event.

2. Error 2 'System.EventHandler' is a delegate type and requires a single 'addressof' expression as the only argument to the constructor.

Can anyone explain what these erros are about and how to deal with them.

Kind Regards

JF

Imports System
Imports System.Windows.Forms

Class MyButtonClass
Inherits Form
Private mrButton As Button

' Constructor method

Public Sub MyButton()
mrButton = New Button()
mrButton.Text = "Click me"
mrButton.Click += New System.EventHandler(MyButtonClickEventHandler)
Me.Controls.Add(mrButton)
End Sub

' Main method

Shared Sub Main()
Application.Run(New MyButtonClass())
End Sub

Private Sub MyButtonClickEventHandler( _
ByVal sender As Object, ByVal e As EventArgs)
mrButton.Text = "You clicked me!"
End Sub


End Class

Answer 1

There are two ways to go about what you are trying to accomplish....first is using the addhandler method:

 

Code Snippet

Imports System
Imports System.Windows.Forms

Class MyButtonClass
Inherits Form
Private mrButton As Button

' Constructor method

Public Sub New()
mrButton = New Button()
mrButton.Text = "Click me"
AddHandler mrButton.Click, AddressOf MyButtonClickEventHandler 

Me.Controls.Add(mrButton)
End Sub

' Main method

Shared Sub Main()
Application.Run(New MyButtonClass())
End Sub

Private Sub MyButtonClickEventHandler( _
ByVal sender As Object, ByVal e As EventArgs)
mrButton.Text = "You clicked me!"
End Sub


End Class

 

Second is to just declare the control with "WithEvents" and use the "Handles" statement:

 

Code Snippet

Imports System
Imports System.Windows.Forms

Class MyButtonClass
Inherits Form
Private WithEvents mrButton As Button

' Constructor method

Public Sub New()
mrButton = New Button()
mrButton.Text = "Click me"
Me.Controls.Add(mrButton)
End Sub

' Main method

Shared Sub Main()
Application.Run(New MyButtonClass())
End Sub

Private Sub MyButtonClickEventHandler( _
ByVal sender As Object, ByVal e As EventArgs)Handles mrButton.Click
mrButton.Text = "You clicked me!"
End Sub


End Class

 

 Edit: after taking a look I've notice that you are getting C# and VB intertwined...the contructor for a VB class should be "New"

 

Answer 2

Thank you, it worked

Though it didn't please me as now I can't trust this guide at all   and I'm starting to get mixed which is VB6, VB.net and finally but not least C# . As this Guide (http://msdn2.microsoft.com/en-us/library/bb330926(VS.80).aspx) tells its for Visual Basic and still it contains that code example:

Code Snippet
Imports System
Imports System.Windows.Forms
 
Class MyButtonClass
       Inherits Form
      Private mrButton As Button
 
      ' Constructor method
 
      Public Sub MyButtonClass()
            mrButton = New Button()
            mrButton.Text = "Click me"
            mrButton.Click += New System.EventHandler(MyButtonClickEventHandler)
            Me.Controls.Add(mrButton)
      End Sub
 
      ' Main method
 
      Shared  Sub Main()
            Application.Run(New MyButtonClass())
      End Sub
 
      ' Event handler method
 
      Private  Sub MyButtonClickEventHandler(ByVal sender As Object, _
                         ByVal e As EventArgs)
            mrButton.Text = "You clicked me!"
      End Sub
End Class

Well, perhaps that's the reason they call it Guide for "Bright Kids" as you have to notice errors they have written to it.

Answer 3

Thank you, it worked

Though it didn't please me as now I can't trust this guide at all   and I'm starting to get mixed which is VB6, VB.net and finally but not least C# . As this Guide (http://msdn2.microsoft.com/en-us/library/bb330926(VS.80).aspx) tells its for Visual Basic and still it contains that code example:

Code Snippet
Imports System
Imports System.Windows.Forms
 
Class MyButtonClass
       Inherits Form
      Private mrButton As Button
 
      ' Constructor method
 
      Public Sub MyButtonClass()
            mrButton = New Button()
            mrButton.Text = "Click me"
            mrButton.Click += New System.EventHandler(MyButtonClickEventHandler)
            Me.Controls.Add(mrButton)
      End Sub
 
      ' Main method
 
      Shared  Sub Main()
            Application.Run(New MyButtonClass())
      End Sub
 
      ' Event handler method
 
      Private  Sub MyButtonClickEventHandler(ByVal sender As Object, _
                         ByVal e As EventArgs)
            mrButton.Text = "You clicked me!"
      End Sub
End Class

Well, perhaps that's the reason they call it Guide for "Bright Kids" as you have to notice errors they have written to it.