C# drawing lines

[Sibuns]

Hey!

I have some trouble with drawing on picturebox in visual studio c#. I want do draw a line between 2 points that i get either with mouse clicks or with inserting coordinates manualy.
So i have created 2 events, picterbox paint event where i made a pen and graphics, and mouse click event where i want to store mouse clicks so i can connect two points. I dont know how to properly store those two clicks. I was doing something wit e.Location but it doesnt register the second click and always stores my first click so i dont draw nothing because of that. So can someone pls tell me what is the best way to store the clicks so i can later use them in g.drawline(p,point1,pont2)...

Ty for your help

[skatamatic]

You will need a flag (boolean member will work) that indicates the first click has been saved, then check this flag in the OnClick event. If the flag is set, save the point to a different location. Clear the flag after the second click has been processed (this is assuming you only want to save 2 points)

[Sibuns]

You mean something like this? I declare 2 points;

Point p1;
Point p2;
bool check=false;

Then in the mouseclick event

{
            if (!check)
            {
                p1 = e.Location;
                
            }

            else
            {
                p2 = e.Location;
                
            }   
           
        }

[skatamatic]

Yep. But after p1 = e.Location you need to set the check flag to true. And after the p2.location you need to actually draw the line

[Sibuns]

Ok here is my code now but it isnt working... It doest draw a line on picturebox.

Point p1;
        Point p2;
        bool check = false;
        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;
            Pen p = new Pen(Color.Black, 1);

            g.DrawLine(p, p1, p2);    
        }

        
        private void pictureBox1_MouseClick(object sender, MouseEventArgs e)
        {

            if (!check)
            {
                p1 = e.Location;
                check = true;
            }

            

            else
            {
                p2 = e.Location;
                
            }

[Momerath]

This is because the Paint method of pictureBox is only called if it has to redraw the PictureBox. Try doing your two clicks, minimize the form then restore it. Add this to the 'else' part of your MouseClick event:

((PictureBox)sender).Refresh();

[Sibuns]

Oh nice is working now. So what do i have to do if i want to draw 2 lines? And every time that there are 2 line drawn, how to i get that if i draw a new 2 lines the old two ones disapears?

[Sibuns]

Ok never mind above post. I figure it out. Now i have another problem. With this code i can draw as many lines as i want... But i would like, that after 2 drawn lines, those lines dissapear and i can draw another 2 lines and so on... And i have one more question about bitmap. I used this:

pictureBox1.Image = new Bitmap(pictureBox1.Width, pictureBox1.Height);

What is the diference between bitmap and normal picture box.

Ty for your help! ;)

Here is the code :

Point p1;
        Point p2;
        List<Point> p1List = new List<Point>();
        List<Point> p2List = new List<Point>();

            
        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            
            Graphics g = e.Graphics;
            Pen p = new Pen(Color.Black, 1);

            

            for (int x = 0; x < p1List.Count; x++)
            {
                g.DrawLine(p, p1List[x], p2List[x]);
            }

            
        }
        
        
        private void pictureBox1_MouseClick(object sender, MouseEventArgs e)
        {

                if (p1.X == 0)
                {
                    p1.X = e.X;
                    p1.Y = e.Y;
                }
                else
                {
                    p2.X = e.X;
                    p2.Y = e.Y;

                    p1List.Add(p1);
                    p2List.Add(p2);

                    pictureBox1.Invalidate();
                    p1.X = 0;
                }
   
        }

[Momerath]

If you want to limit the number of points just make sure your List object doesn't have too many in it. Put a check right after you add your two new points to see how large the Count property is, if it is over 4 then remove the first one (index 0) twice.

[Sibuns]

You mean something like this:

if (p2List.Count == 2)
            {
                p1List.Clear();
                p2List.Clear();
            }

The problem here is when i have count ==2 it doest draw 2 lines but it clear all lines right after i draw the second line. But if i have count > 2 then i need to draw the third line to make all go away.

[Momerath]

No, clear removes all items. I said remove the index zero item twice. RemoveAt

[Sibuns]

You meant like this:

if (p2List.Count > 2)
                    {
                        p2List.RemoveAt(0);
                    }

                    if (p1List.Count > 2)
                    {
                        p1List.RemoveAt(0);
                    }

But if i use this code i line always stays drawn.
And i want program to work like this. I draw 2 lines on picturebox, and when i star to draw the third line, both lines that were drawn beofre dissapears and the screen is empty..

[Sibuns]

Anyone?