clearing the image in a picturebox

Question

'i using this code in the piicturebox1_paint

myusercolor=(sysytem.drawing.color.black)
myalpha=100
using g as graphics=graphics.fromimage(picturebox1.image)
    g.clear(color.white)
    dim currentpen as object=new pen(color.fromargb(myalpha,myusercolor),mypenwidth)
    g.drawpath(ctype(currentpen,pen),mousepath)
end using

'using in the form_load '
picturebox1.image=new bitmap(.....)

'in the clearbutton_click '
picturebox1.image=nothing

by this code i have a problem that when i click the clear button the picturebox is cleared.but in the picturebox's mouseover the last drawn picture will appear.so i cant draw a new image ..

Answer 1

It's a guess, but I think that mousepath contains the "drawing" that the user has made. When initializing a new image (probably in the clearbutton_click event handler) you will also need to clear that data:

If Not mousepath Is Nothing Then
    mousepath.Dispose()
End If
mousepath = new GraphicsPath()

---

As a side note, not directly related to your question, I would suggest two improvements in how the Pen is handled. Look at the following two code lines (from your sample above):

dim currentpen as object=new pen(color.fromargb(myalpha,myusercolor),mypenwidth)
g.drawpath(ctype(currentpen,pen),mousepath)

This first creates a new Pen and stores it in the object variable currentpen. Since currentpen is declared as object, you need to cast it to Pen when passing it to DrawPath. If you instead declare currentpen as a Pen you don't need to do that cast. Also, Pen implements IDisposable so you should either call Dispose on it, or wrap it into a using block:

Using currentpen as Pen = new Pen(Color.FromArgb(myalpha,myusercolor),mypenwidth)
    g.drawpath(currentpen,mousepath)
End Using

Answer 2

You're drawing in the Picturebox1_paint event? This will fire every time the control is affected by such things as moving the form or in this case a mouse moving over it. You should be drawing outside that event, but where depends on what you're trying to do.