Question

I have code that highlights the current textbox in focus in order to provide a visual cue to the user. My question is, if I had 10 forms with textboxes and I wanted to provide this same code to them all. Would I have to duplicate it or can I use a global method? If so, an example would be very helpful. Thanks.

The code is as follows.

Private Sub FocusChanged(ByVal sender As Object, ByVal e As EventArgs)
    Dim txt As TextBox = sender
    If txt.Focused Then
        txt.Tag = txt.BackColor
        txt.BackColor = Color.AliceBlue
    Else
        txt.BackColor = txt.Tag
    End If
End Sub
Private Sub CreateAccount_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    For Each ctrl As TextBox In Me.Controls.OfType(Of TextBox)()
        AddHandler ctrl.GotFocus, AddressOf FocusChanged
        AddHandler ctrl.LostFocus, AddressOf FocusChanged
        ctrl.Tag = ctrl.BackColor
    Next
End Sub

Answer 1

If you want to add this behavior to all TextBox controls, you’re better off deriving your own class from the TextBox class, and override the OnGotFocus and OnLostFocus methods to set the properties accordingly.

Here’s how:

Public Class MyTextBox
    Inherits TextBox

    Protected Overrides Sub OnGotFocus(e As System.EventArgs)
        MyBase.OnGotFocus(e)
        Me.Tag = Me.BackColor
        Me.BackColor = Color.Aqua
    End Sub

    Protected Overrides Sub OnLostFocus(e As System.EventArgs)
        MyBase.OnLostFocus(e)
        Me.BackColor = Me.Tag
    End Sub
End Class

EDIT: forgot to mention that after adding that class to your project, rebuild the solution, and if it compiles without errors, then your new TextBox class show show up in the VS ToolBox. You can then simply drag & drop onto your form just as any control.

Cheers