Issues with Client size function - vb.net

Question

I am working on a Windows Form and struggling to draw lines that are centered, can I get some help with the solution for this. Thank you.
Dim iFormHeight As Integer = Me.ClientSize.Height
Dim iFormWidth As Integer = Me.ClientSize.Width
Dim centreX As Integer = Me.ClientSize.Width \ 2
Dim centreY As Integer = Me.ClientSize.Height \ 2
Dim compteur As Integer = 0
Dim x1 As Integer = centreX - 50
Dim y1 As Integer = centreY - 50
Dim x2 As Integer = centreX + 50
Dim y2 As Integer = centreY + 50
Dim g As Graphics = CreateGraphics()
Dim pen1 As New Pen(Color.Red)
Private Sub Form3_Paint(sender As Object, e As PaintEventArgs) Handles MyBase.Paint
g.DrawLine(pen1, 0, y1, x1, y1)
g.DrawLine(pen1, x1, 0, x1, y1)
g.DrawLine(pen1, x2, y1, x2, 0)
g.DrawLine(pen1, x2, y1, iFormWidth, y1)
g.DrawLine(pen1, 0, y2, x1, y2)
g.DrawLine(pen1, x1, y2, x1, iFormHeight)
g.DrawLine(pen1, x2, y2, x2, iFormHeight)
g.DrawLine(pen1, x2, y2, iFormWidth, y2)
pen1.Dispose()
g.Dispose()
End Sub
Private Sub Form3_Load(sender As Object, e As EventArgs) Handles MyBase.Load, MyBase.Resize
hautgauche.Location = New Point(x1 - basdroit.Width, y1 - basdroit.Height)
basdroit.Location = New Point(x2, y2)
hautdroit.Location = New Point(x2, y1 - basdroit.Width)
basgauche.Location = New Point(x1 - basdroit.Height, y2)
Timer1.Start()
End Sub
what i get
what i want