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Calling a function that involves PaintEventArgs when a button is clicked

Sorry if this has been asked before.
I was working on a simple connect 4 game in C# windows forms as I haven't done any work involving graphics before. To do this I need the program to draw circles when a button is pressed however I don't know how to call the function to do so.
public void printToken(PaintEventArgs pe, int x)
{
Graphics g = pe.Graphics;
Pen blue = new Pen(Color.Blue);
Pen red = new Pen(Color.Red);
Rectangle rect = new Rectangle(50 + ((x-1) * 100), 50, 50, 50);
g.DrawEllipse(blue, rect);
}
private void button1_Click(object sender, EventArgs e)
{
printToken(null, 1);
}
The null in place is just a placeholder as obviously that will not work.
Any and all help is appreciated.

Typically in a Windows Forms application where you want to do custom drawing, you either draw directly on a Form or PictureBox in the Paint event handler or create a subclass of Control in which you override the OnPaint method. In the Paint event handler or OnPaint, you draw everything (i.e. not just one circle, but all the circles). Then when your underlying data structure changes, indicating that you need a repaint, you call Invalidate() on the control, which marks it as needing redraw, and on the next pass through the event loop, your Paint event handler will run or your OnPaint method will be called. Within that method, you'll have the PaintEventArgs object you need to get a Graphics object with which to do your drawing. You don't want to "draw once and forget" (e.g. when a button is clicked) because there are all sorts of things that can cause your control to need to repaint itself. See this question and answer for more details on that.
Edit: here's some hand-holding in response to your comment. (It was going to be a comment but it got too long.)
If I assume for the moment that you're starting with a blank Form in Visual Studio's Windows Forms Designer, the quickest way to get going would just be to select the Form, and in VS's Properties pane, click the lightning bolt toolbar button to view the form's events. Scroll down to the Paint event and double-click anywhere in the blank space to the right of the label. That will wire up a Paint event handler for the form and take you to the newly added method in the form's code file. Use the PaintEventArgs object called e to do your drawing. Then, if you need to change what gets drawn upon some button click, in your click handler change the data that determine what gets drawn (e.g. positions and colors of of the playing pieces) and, when you're done, call Invalidate().

If you add a UserControl representing a single chip to your form, and override the OnPaint method and put the coloring code into that event, then the Graphics object will not be null when the Paint event fires.
To kick off the paint of the UserControl, either call the Refresh method or InvalidateRectangle method - either will fire the OnPaint method.
Make sure to call up the class hierarchy to the OnPaint first, to make sure that the background of the object is drawn first:
protected override void OnPaint(PaintEventArgs e) {
base.OnPaint(e);
Graphics g = e.Graphics;
Pen blue = new Pen(Color.Blue);
Pen red = new Pen(Color.Red);
Rectangle rect = new Rectangle(50 + ((x-1) * 100), 50, 50, 50);
g.DrawEllipse(blue, rect);
}

Background Panel Windows Form

I hope you can help me with this problem, attached videos to explain in a simpler way.
First example
Panel (has a textured background) with labels (the labels have a png image without background)
Events: MouseDown, MouseUp and MouseMove.
As you will notice in the video to drag the label the background turns white panel and regains its background image when I stop dragging the label
Panel controls have a transparent background as property, but changing the background with any color, let the problem occurred related to the substance, I do not understand why this happens and how to fix less.
Second Example
Contains the above, with the only difference that the panel controls instead of having transparent background, I chose black color for that property

You have to use double buffer and you don't have to stop using an image on the background, you can have everything running smoothly.
You have a couple of ways to do this, the fast way (not enough most of the time) is to enable doublebuffer of the panel.
The "slow" but better way is to do your own Double Buffer using a Bitmap object as a buffer.
This example creates a "side buffer" and accepts an image as parameter and draws it using created buffer.
public void DrawSomething(Graphics graphics, Bitmap yourimage)
{
Graphics g;
Bitmap buffer = new Bitmap(yourimage.Width, yourimage.Height, graphics);
g = Graphics.FromImage(buffer);
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
g.DrawImage(yourimage, 0, 0);
graphics.DrawImage(buffer, 0, 0);
g.Dispose();
}
Call this on your OnPaint event.
BTW... this is just a double buffer example.
Cheers

Change DoubleBuffered to true for both form and panel. I think that should solve your problem.

this is totally normal, because System.Windows.Forms.Control based items were not designed to do this kind of advanced Graphics operations.
in fact the reason that this effect happens here, is that when you assign any value other than 255 to the alpha component of a control BackColor, the form does the following when you change the control size or position:
it sets the new control position
it redraws the parent control
it gets the background of the control's parent as an image
it draws acquired image into the control body to seem as if the control is transparent
the control body gets drawn on top of the previously drawn background
the control children are drawn
* this is is a simplified explanation for the sake of illustration to deliver the idea
steps 1, 2 are responsible for the flickering effect that you see.
but you have two ways to solve this,
-the first is some kinda advanced solution but it's very powerful, which is you would have to create a double buffered custom control that would be your viewport.
the second is to use WPF instead of windows forms, as WPF was designed exactly to do this kind of things.
if you can kindly provide some code, i can show you how to do both.

How to delete a drawn circle in c# windows form?

I have drawn a circle in windows form
Pen pen = new Pen(Color.Black, 3);
Graphics gr = this.CreateGraphics();
gr.DrawEllipse(pen, 5,5,20,20);
How to delete it...

You have to clear your Graphic:
Graphics.Clear();
But all drawn figures will be cleared. Simply, you will then need to redraw all figures except that circle.
Also, you can use the Invalidate method:
Control.Invalidate()
It indicates a region to be redrawn inside your Graphics. But if you have intersecting figures you will have to redraw the figures you want visible inside the region except the circle.
This can become messy, you may want to check out how to design a control graph or use any graph layout library.

You can invalidate the draw region you want to refresh for example:
this.Invalidate();
on the form...

Assuming you're subscribing to the Paint event or overriding the protected OnPaint routine, then you will need to perform something like this:
bool paint = false;
protected override void OnPaint(object sender, PaintEventArgs e)
{
if (paint)
{
// Draw circle.
}
}
Then when you want to stop painting a circle:
paint = false;
this.Invalidate(); // Forces a redraw

You can make a figure of same dimensions using the backColor of your control in which you are drawing
use after your code to clear your figure.
Pen p = new Pen(this.BackColor);
gr.DrawEllipse(p, 5,5,20,20);

In fact, you can delete your circle and nothing but your circle.
Everything you need is something like a screenshot of the "before state" of the area you want to clear, to make a TextureBrush from it. You can achieve that step by something like this:
Bitmap _Background = new Bitmap(this.Width, this.Height);
Graphics.FromImage(_Background).CopyFromScreen(this.Left, this.Top, 0, 0, this.Size);
The first line will give you a bitmap in your windows forms size. The second line will save a screenshot of it in the _Background-bitmap.
Now you create a TextureBrush out of it:
Brush brsBackground = new TextureBrush(_Background);
The next thing you need are the dimensions of your circle, so you should save them into a variable, if they are not a fix value. When you got them at hand, you can clear the specific area like this:
Graphics gr = this.CreateGraphics();
gr.FillEllipse(brsBackground, 5, 5, 20, 20); // values referred to your example
Done!
Even complex figures are able to be deleted by this, like a GraphicsPath for example:
GraphicsPath gp = new GraphicsPath(); // any kind of GraphicsPath
gr.FillRegion(brsBackground, new Region(gp));

You don't "delete" it per se, there's nothing to delete. It's a drawing, you draw something else over it or you can call the Graphics.Clear() method.

If u are using Invalidate() and is not working, make a panel.Refresh().
That will work on you.

just make another control with the attributes etc. that you want, make the visibility to false and set the region of the control to the other control like this:
pen.Region = pen2.Region;

It is very simple to delete a drawn circle from c.
There is only four steps:-
Open turbo app
go to the command where you had drawn the circle
drag the command
click on delete button

c# - clear surface when resizing

I'm trying to build my own custom control for a windows forms application in C#.Net. Currently I paint some rectangles and other graphic elements using the paint event.
When I now resize the app form to fit the desktop size, all elements are repainted (which is exactly the behaviour I need) but the old one's are shown in the background.
Here's what I'm doing by now:
Pen penDefaultBorder = new Pen(Color.Wheat, 1);
int margin = 5;
private void CustomControl_Paint(object sender, PaintEventArgs e) {
CustomControl calendar = (CustomControl)sender;
Graphics graphics = e.Graphics;
graphics.Clear(Color.WhiteSmoke);
graphics.DrawRectangle(penDefaultBorder, margin, margin, calendar.Width - margin * 2, calendar.Height - margin * 2);
//...
}
Neither the graphics.Clear, nor adding a graphics.FillRectangle(...) will hide the old rectangle from the surface.
Ideas? Thank you all.

Paint events usually don't request an update for the entire canvas, just the area specified in the PaintEventArgs. I'm guessing what's happening is that only the newly-exposed regions of the canvas are being passed in the PaintEventArgs.
This one of the reasons that you shouldn't do any rendering in the Paint event. You should render to an offscreen bitmap - a buffer - and copy from that buffer to the control's canvas in the Paint event.
Searching for "double buffering" here or on Google will give you many examples of the technique.

Have you tried .Invalidate() to cause the form to redraw?

How do I make a form transparent while keeping the controls fully visible?

I would like to have a form in which the controls on the form are fully visible but the form itself is invisible. If I change the form's Opacity, this makes both the form and the controls on it semi-transparent, so this doesn't work.
I can't do this by setting the form's TransparencyKey, since I have a PictureBox on the form. If the image in the PictureBox happens to contain pixels that match the TransparencyKey, they appear as openings in the form, which I don't want.

TransparencyKey is the only way to get this. Pick the right color. Color.Fuchsia has a long tradition of being the color of choice, going back to the early days of Win32 development. Assault your eye with it to see its merits.

With the caveat that I've never used it, just ran across it once, thought "neat!" and moved on...
Look into System.Drawing.Drawing2D.GraphicsPath and setting the form's Region property. I added two buttons to the basic Windows forms application:
public Form1()
{
InitializeComponent();
Rectangle r1 = new Rectangle(button1.Location, button1.Size);
Rectangle r2 = new Rectangle(button2.Location, button2.Size);
GraphicsPath gp = new GraphicsPath();
gp.AddRectangle(r1);
gp.AddRectangle(r2);
this.Region = new Region(gp);
}
I've approximated the shape of the button with a rectangle; with this code, you can see the form background color at the buttons' corners. You'll need to work out the enclosing path for each of your controls and add them to the path individually. You'll need to take into account any offset introduced by the form title bar or border style.
Update: I did some investigation and have a couple of possible approaches for the problem:
Using the GraphicsPath method, set pictureBox.Visible to False if there is no image loaded.
When you load an image into the picture box, analyze the image to get a list of all the colors in it, then randomly generate one that isn't. Set the form's BackColor and TransparencyKey properties to match this new color, Hans Passant's answer.