How do I create an eventhandler for 32 programmatically created checkboxes (winforms) ?

How do I create an eventhandler for 32 programmatically created checkboxes (winforms) ?

• leovernazza

  Here's an example using programatically creating textboxes and hooking up the controls to the same event handle programatically. In this example it creates some textboxes - you change the text in them and nothing happens except text changes - click the button to hookup the event handlers for these controls and then change the text in the same boxes and a messagebox will appear every time you change the text in one of the boxes.

  The bold italic text is the event handler and hookup code which can easily be applied to any other controls or event handlers.

  Public Class Form1

  Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
  For i As Integer = 21 To 30
  Dim x As New TextBox
  x.Name = "TxtAdded" & i.ToString
  x.Top = i * 18
  x.Left = 30
  x.Visible = True
  Me.Controls.Add(x)
  Next
  End Sub

  Private Sub BtnAddHandler_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
  For Each c As Control In Me.Controls
  If TypeOf (c) Is TextBox Then
  AddHandler c.TextChanged, AddressOf TextBox_TextChanged
  End If
  Next
  End Sub

  
  Private Sub TextBox_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox3.TextChanged
  MsgBox(CType(sender, TextBox).Name)
  End Sub
  End Class
  

  
  

• Quirk

  ahh I see... so the Addhandler creates this 'generic' textchanged handler for all textboxes created. And then you use the CType(sender to determine which one it is. Great! thank you! I'll give it a whirl. -g
  

• yeos_lee

  Thank you. Would the Handles TextBox3.TextChanged need to be changed to include all (in this case) textboxes This seems to be hardcoded and assumes I would know ahead of time how many controls I created Handles textbox1.changed,textbox2.changed,textbox3.changed.....etc....
  

• Krutika

  Sure the addhandler is the way to hookup controls to methods. As long as the signature on the method matches the signature of the event then you are good to go.

  So in this case I create a control and method for a textbox event to ensure that I got the correct method with signatures for the eventhandler - and then programatically hooked the controls to the method using eventhandler.

  The handles clause does pretty well the same thing but requires you to specify them at design time and not programatically at runtime.

  
  

• ZeePrime

  You can remove the handles clause of the method - the only reason it was there was I used one of the controls of the type I wanted to hookup to ensure that the signature was correct.

   Public Class Form1

      Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
          For i As Integer = 21 To 30
              Dim x As New TextBox
              x.Name = "TxtAdded" & i.ToString
              x.Top = i * 18
              x.Left = 30
              x.Visible = True
              Me.Controls.Add(x)
          Next
      End Sub

      Private Sub BtnAddHandler_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
          For Each c As Control In Me.Controls
              If TypeOf (c) Is TextBox Then
                  AddHandler c.TextChanged, AddressOf TextBox_TextChanged
              End If
          Next
      End Sub

  
      Private Sub TextBox_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
          MsgBox(CType(sender, TextBox).Name)
      End Sub
  End Class
  

  
  
• How do I create an eventhandler for 32 programmatically created checkboxes (winforms) ?