在没有视觉工作室设计师的情况下绘制形状。 形状未显示且事件未触发

Question

I am simply trying to draw some shapes without the use of visual studio functionality, most tutorials use that, and I am reasonbly sure that the coding is different because of that, so last resort was to ask here.

Following some guides on forms, that didn't use any visual studio (and yeah, I know that it is much easier with it, but using such things has screwed me in the past, so wanna learn without) I got the form made and such, but when it came to actually drawing shapes, I hit a wall.

I did a bit of debugging, from what I have been able to determine, the event does not fire at all. And the graphics code in the main function does nothing, just a blank form shows up. I tried a couple of variations on both the in-main code, and the event code, which is visible in the code, I also tried using a variant of the event that used a "sender" argument, no idea if changing that made any difference, none of them fired anyways.

using System;
using System.Windows.Forms;
using System.ComponentModel;
using System.Drawing;
using System.Workflow.ComponentModel;

class Genetics : Form
{

    public static Form form1;
    static void Main(string[] args)
    {

        form1 = new Form();
        form1.Size = new Size(800, 800);

        Pen blackpen = new Pen(Color.Black, 10);
        Graphics G = form1.CreateGraphics();

        G.DrawRectangle(blackpen, form1.Width - form1.Width / 2, form1.Width - form1.Width / 2, 300, 300);

      form1.CreateGraphics().DrawRectangle(blackpen, form1.Width -    form1.Width / 2, form1.Width - form1.Width / 2, 300, 300);

        Application.Run(form1);


    }

    protected override void OnPaint(PaintEventArgs e)
    {        
        Graphics graphics;
        graphics = form1.CreateGraphics();

        Pen mypen = new Pen(Color.Black, 5);

        graphics.DrawLine(mypen, 20, 20, 200, 210);

        e.Graphics.DrawRectangle(mypen, 20, 20, 200, 210);

    }


}

I don't get any errors or anything, it just... Doesn't do anything, other than shows the form, but that is a bit of a bare minimum.

I know this is probarbly easy to fix, but again, all tutorials used visual studio forms, and unsure if the code was different. Since I have tried straight up copying that code and it gave me errors, I assume I am correct, but not 100% sure. And I am reasonbly experienced, I am just used to writing in unity, the process of going from there to pure code has been difficult for me though.

Answer 1

Just in case someone other than me was looking for this, the problem was two main things: 1, the events weren't connected to anything, so I needed to add a line like this:

[Form variable].[form event] += new PaintEventHandler([Class].[Method with an object sender and an event argument]
//Example of that
form1.Paint += new PaintEventHandler(Genetics.Paint);

Without this, nothing will happen since the methods and events aren't connected.

2, mostly a repeat of the comments, I needed to have all the draw functions in events, since they won't have anything to draw to, before the application is actually run. Then it's just a matter of invalidating the code inside those events, to force the form to be redrawn.