How to change the TextBox border color when certain event is true?

[ak24]

Hello...

I want to change the TextBox border color if certain event is true.

For example, in a GroupBox, there is a TextBox and a Button.

If the TextBox is empty, and I click the button,
I want the TextBox border color to change to red.

If the TextBox is not empty, I want the border color to remain unchanged.

How do I change the TextBox border color on a certain event?

[Unhnd_Exception]

Use the Textbox's parent paint event to draw the border. You need to set the textbox's region to minus its border for it to show up.

The code will toggle a red border around a text box by pressing a button.

Its hard coded for a 3d border size

Private Sub GroupBox1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles GroupBox1.Paint

        'If the textbox's region hasn't been set then this will draw behind
        'the textbox.
        Dim p As New Pen(Color.Red, 2)
        e.Graphics.DrawRectangle(p, New Rectangle(TextBox1.Location + New Size(1, 1), TextBox1.Size - New Size(2, 2)))
        p.Dispose()

    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        'Set the region to the textbox's size - its border size.
        If TextBox1.Region Is Nothing Then
            TextBox1.Region = New Region(New Rectangle(2, 2, TextBox1.Width - 4, TextBox1.Height - 4))
        Else
            TextBox1.Region = Nothing
        End If
     
    End Sub

[ak24]

This code works perfect!

Thank you.