Override Paint Method for a PaintBox

Question

Hi I am trying to write a program where multiple instances of a class will draw themselves onto a PictureBox. (If there is a better control to use then that would be useful to know!). The paint method in the main form looks like : public virtual void pbWorld_Paint( object sender System.Windows.Forms.PaintEventArgs e) {... The override in the class of which multiple instances will occur is : public override void pbWorld_Paint( object sender System.Windows.Forms.PaintEventArgs e) { // Create a local version of the graphics object for the PictureBox. Graphics g = e.Graphics; System.Drawing.Pen pen = new Pen(System.Drawing.Color.Black 1); g.DrawRectangle(pen posX posY 2 2); } What I need the program to do is everytime a new instance is created update the main PictureBox with the new object and then everytime the position of that object changes update the area around the object (so as not to redraw the whole screen). I assume that I need to create a specific event for this and link it to the overridden paint method?! I hope I have included enough info here - if not just let me know what else you need to know to help me out on this one! Many thanks Bertie.

Chris Bertrand · Answer

Thanks for the reply Mike - and I have now changed to it painting on the form. However my question still remains - how do I override the OnPaint method so that it will draw on creation of the object and then whenever it's position changes? I don't want to have to have the object carry a graphics property with it so how do I go about getting the form's surface for the object to draw on? The object is in it's own class under the same namespace. It has a method to update it's position and what I want to be able to do is when that position is altered fire a paint event from within the object's move method. (And also in it's constructor on creation). My thought was to create an event handler and event args and set it up that way. But when I try and do this it complains that the eventhandler doesn't have the right parameters - because I'm using my own eventargs and not System.Windows.Forms.PaintEventArgs. So this is roughly how it looks : PaintCode.cs - public class ObjectPaintEventArgs : EventArgs { int left; int top; int right; int bottom; public ObjectPaintEventArgs(Rectangle r System.Windows.Forms.PaintEventArgs e) { left = r.Left; top = r.Top; right = r.Right; bottom = r.Bottom; } } public delegate void ObjectPaintEventHandler( object sender ObjectPaintEventArgs e); agent.cs - public event ObjectPaintEventHandler paintAgent; public Agent( int x int y int village) {... ObjectPaintEventArgs paintAgentEventArgs = new ObjectPaintEventArgs( new Rectangle(x y 2 2)); paintAgent += new ObjectPaintEventHandler(MainForm_Paint); paintAgent( this  paintAgentEventArgs); ... } public override void MainForm_Paint( object sender System.Windows.Forms.PaintEventArgs e) {... }

Mike Gold · Answer

Not sure you want to necessarily do this with a picture box. You can just paint directly on the form in the area you want to update. As long as you only invalidate the region in which you want updated and not the whole form it should only paint on that clip region.