Using Graphics.Drawline

[kylek]

How do I use the Graphics.Drawline function in the middle of another function on my form.

What I want to do is just draw an X across part of my form, but where, and what size changes.

I think my problem is in creating the graphics object. What I did was create a global graphics variable called '_graphics' and in the myBase.Paint event I set that global variable to the forms graphics object:

Private Sub Panel_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles MyBase.Paint          
     _graphics = e.Graphics      
End Sub

Then in my function I create a pen, and try to draw my two lines:

Private Sub DrawBlock(ByVal Cir As Circuit)
          Dim pen As Pen = New Pen(Color.Black, 1)
          
          Dim _Left As Integer = Cir.Left
          Dim _Right As Integer = Cir.Left + Cir.Width
          Dim _Top As Integer = Cir.Top
          Dim _Bottom As Integer = Cir.Top + Cir.Height  
 
          _graphics.DrawLine(pen, _Left, _Top, _Right, _Bottom)
          _graphics.DrawLine(pen, _Left, _Bottom, _Right, _Top) 
End Sub

When it gets to the first _graphics.DrawLine(...) I get an error stating "Invalid Paramater Used".

Any Ideas? I'm likely just using the graphics class wrong.