Handling all textbox event in one Handler

Question

I do know how to handle event of textboxes in my form. But want to make this code shorter because I will 30 textboxes. It\'s inefficient to use this:

Private         


        

Answer 1

Say If you are having that 30 textboxes inside a panel(PnlTextBoxes), Now you can create handler for your textboxes dynamically like this below

For each ctrl in PnlTextBoxes.controls
 If TypeOf ctrl is TextBox then
   AddHandler ctrl.TextChanged, AddressOf CommonClickHandler
 end if
Next


Private Sub CommonHandler(ByVal sender As System.Object, _
ByVal e As System.EventArgs)

      MsgBox(ctype(sender,TextBox).Text)

End Sub

Answer 2

If you have created very Textbox with the Designer, I don't think there is a better method.

But, if you have created the Textboxes dynamically, you should AddHandler in this way:

For i = 0 to 30
    Dim TB as New Texbox
    AddHandler TB.TextChanged, TextBox1_TextChanged
    'Set every Property that you need
    Me.Controls.Add(TB)
Next

Answer 3

The best way would be to inherit from TextBox, override its OnTextChanged method to add your custom handling code, and then use that on your form(s) instead of the built-in TextBox control.

That way, all of the event handling code is in one single place and you increase abstraction. The behavior follows and is defined within the control class itself, not the form that contains the control. And of course, it frees you from having a bunch of ugly, hard-to-maintain Handles statements, or worse, slow and even uglier For loops.

For example, add this code defining a new custom text box control to a new file in your project:

Public Class CustomTextBox : Inherits TextBox

    Protected Overridable Sub OnTextChanged(e As EventArgs)
        ' Do whatever you want to do here...
        MsgBox(Me.Text)

        ' Call the base class implementation for default behavior.
        ' (If you don't call this, the TextChanged event will never be raised!)
        MyBase.OnTextChanged(e)
    End Sub

End Class

Then, after you recompile, you should be able to replace your existing TextBox controls with the newly-defined CustomTextBox control that has all of your behavior built in.

Answer 4

You can use Controls.OfType + AddHandler programmatically. For example:

Dim textBoxes = Me.Controls.OfType(Of TextBox)()
For Each txt In textBoxes
    AddHandler txt.TextChanged, AddressOf txtTextChanged
Next

one handler for all:

Private Sub txtTextChanged(sender As Object, e As EventArgs)
    Dim txt = DirectCast(sender, TextBox)
    Select Case txt.Name
        Case "TextBox1"
            MsgBox(txt.Text)
        Case "TextBox2"
            MsgBox(txt.Text)
    End Select
End Sub