Center form on screen or on parent

Question

Since built in functionality for positioning forms in VB.NET are not always suitable to use I try to make my sub to do that.

But I missed something...

Answer 1

I had the problem with StartPosition = CenterParent not working. I solved it calling the form with .ShowDialog() instead of .Show():

' first you should set your form's Start Position as Center Parent
Private Sub button_Click(sender As Object, e As EventArgs) Handles button.Click
    MyForm.ShowDialog()
End Sub

Answer 2

This might also be of use:

    myForm.StartPosition = FormStartPosition.CenterParent
    myForm.ShowDialog()

You can also use FormStartPosition.CenterScreen

Answer 3

The code is just wrong. It is also essential that this code runs late enough, the constructor is too early. Be sure to call it from the Load event, at that time the form is properly auto-scaled and adjusted for the user's preferences, the StartPosition property no longer matters then. Fix:

Public Shared Sub CenterForm(ByVal frm As Form, Optional ByVal parent As Form = Nothing)
    '' Note: call this from frm's Load event!
    Dim r As Rectangle
    If parent IsNot Nothing Then
        r = parent.RectangleToScreen(parent.ClientRectangle)
    Else
        r = Screen.FromPoint(frm.Location).WorkingArea
    End If

    Dim x = r.Left + (r.Width - frm.Width) \ 2
    Dim y = r.Top + (r.Height - frm.Height) \ 2
    frm.Location = New Point(x, y)
End Sub

Incidentally, one of the very few reasons to actually implement the Load event handler.

Answer 4

I know this is an old post and this doesn't directly answer the question, but for anyone else who stumbles upon this thread, centering a form can be done simply without requiring you to write your own procedure.

The System.Windows.Forms.Form.CenterToScreen() and System.Windows.Forms.Form.CenterToParent() allow you to center the a form in reference to the screen or in reference to the parent form depending on which one you need.

One thing to note is that these procedures MUST be called before the form is loaded. It is best to call them in the form_load event handler.

EXAMPLE CODE:

  Private Sub Settings_Load(sender As Object, e As EventArgs) Handles Me.Load

    Me.CenterToScreen()

    'or you can use 

    Me.CenterToParent()

End Sub