Need some help please :)

[kasavien]

Hi i have the piece of code below which is supposed to draw lines, it isn't complete but should at least draw lines between the points in _currentLinks

        protected override void OnPaint(PaintEventArgs e)
        {
            Graphics graphics = e.Graphics;
            drawNetwork(graphics, this.Width, this.Height);
        }

        private void drawNetwork(Graphics graphics, int width, int height)
        {
            if (this._currentNodes.Count > 0)
            {
                foreach (Node node in this._currentNodes)
                { 
                
                }
            }
            if (this._currentLinks.Count > 0)
            {
                foreach (Link link in this._currentLinks)
                {
                    Pen linkPen = new Pen(Color.Blue);
                    linkPen.Width = 5;
                    graphics.DrawLine(linkPen, link.start, link.end);
                    linkPen.Dispose();
                }
            }
        }

The problem is it doesn't draw anything, i've debugged it as best i know how and it goes through each of the "link"s in "_currentLinks" and goes through the drawline part but nothing appears on screen. Is there something obvious that i have missed. If someone can help i'd be very grateful!

Many thanks

Andy

edit: i aren't using width and height yet, they're there for future use at the moment

[stytagm]

Does the draw function work if you simplify it? Ie, get rid of the loops, and try and get the Draw statement working with some hard coded coords. Then slowly build the other functionality back in.

PS what language is this? C#? Java?

[kasavien]

Sorry yeah forgot to say, it's written in c#, if i call the draw function from somewhere else it works and draws the lines correctly. The only thing i can think that it might be is that it's not drawing on the correct surface.

edit: or could i be drawing it on the correct surface just not within the right bounds, i've tried to check this through debugging and it doesn't appear to be the case since the coordinates it's drawing seem to be less than the width and height.

[TheAnimus]

C#, the dispose is the give away!

look at using. Always use using, as it stands any exceptions can cause leaks. ie

using (Pen pen = new Pen(Color.Blue) {
//.... use the pen obj here ....
}// the .Dispose is automatically closed, even if an exception occurs

there is also no point doing the .Count > 0 bit, as foreach will gracefully simply not run if there is nothing to enumerate. (as long as its not null, but .Count would cause the same nullreferenceexception).

so, odds are the values in the links collection are wrong, breakpoint on the drawline, and have a look at the co-ords been used.

either that or post the required code.

[kasavien]

Hi, thanks for all your help, i sorted it in the end. I noticed that when i minimised and restored the screen the points were being drawn, so as it turned out i needed to refresh the screen after a draw. I also changed my code to start using the "using" keyword as TheAnimus suggested.

Thanks

Andy

[yamangman]

Well I was going to suggest that, followed by 'is the background blue'?