Код
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Windows;
using System.Windows.Input;
using System.Threading;
using System.Runtime.InteropServices;


namespace Grafa
{
public partial class Form1 : Form
{
bool is_press = false;
int cur_counter = 0;
int counter = 0;
Ellipsoid[] mas = new Ellipsoid[100];

Graphics grafa_1;
Pen pen_1 = new Pen(Color.Black);
public Form1()
{
InitializeComponent();
grafa_1 = Graphics.FromHwnd(pictureBox1.Handle);
for (int i = 0; i < 100; i++)
{
mas[i] = new Ellipsoid(5555, 5555);
}
}

private void button1_Click(object sender, EventArgs e)
{
counter++;
int pic_width = pictureBox1.Width / 2;
int pic_height = pictureBox1.Height / 2;
Random random_1 = new Random();
int rand_width = random_1.Next(0, pic_width);
int rand_height = random_1.Next(0, pic_height);
mas[counter] = new Ellipsoid(rand_width, rand_height);
grafa_1.DrawEllipse(pen_1, rand_width, rand_height, 100, 100);
}

private void toolStripMenuItem2_Click(object sender, EventArgs e)
{
pen_1.Width = 1;
}

private void toolStripMenuItem3_Click(object sender, EventArgs e)
{
pen_1.Width = 5;
}

private void toolStripMenuItem4_Click(object sender, EventArgs e)
{
pen_1.Width = 10;
}

private void сплошнаяToolStripMenuItem_Click(object sender, EventArgs e)
{
pen_1.DashPattern = new float[] {1f};
}

private void пунктирнаяToolStripMenuItem_Click(object sender, EventArgs e)
{
pen_1.DashPattern = new float[] { 2f, 1f };
}

private void цветФигурыToolStripMenuItem_Click(object sender, EventArgs e)
{
if (colorDialog1.ShowDialog() == DialogResult.OK)
{
pen_1.Color = colorDialog1.Color;
}
}

public bool Is_Detect(MouseEventArgs e)
{
// Детектирование, кликнули ли мы по какой-нибудь окружности
for (int i = 0; i < 10000; i++)
{
if ((mas[i].width_ <= e.X) && (e.X <= (mas[i].width_) + 100) && (mas[i].height_ <= e.Y) && (e.Y <= (mas[i].height_ + 100)))
{
return true;
}
}
return false;
}

public int GetEllipsoidIndex(MouseEventArgs e)
{
// Определение индекса выделенной окружности
for (int i = 0; i < 100; i++)
{
if ((mas[i].width_ <= e.X) && (e.X <= (mas[i].width_) + 100) && (mas[i].height_ <= e.Y) && (e.Y <= (mas[i].height_ + 100)))
{
return i;
}
}
return -1;
}

private void Form1_Load(object sender, EventArgs e)
{

}

[DllImport("user32.dll")]
public static extern short GetAsyncKeyState(System.Windows.Forms.Keys vKey);

private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
// Мышка зажата
// Детектирование, кликнули ли мы по какой-нибудь окружности
is_press = true;

if (Is_Detect(e))
{
int n = GetEllipsoidIndex(e);

int p_x = e.X;
int p_y = e.Y;
int p_x_new;
int p_y_new;
while(is_press == true)
{
Int16 state = GetAsyncKeyState(Keys.LButton);
if ((state & 0x8000) == 0)
is_press = false;

p_x_new = Cursor.Position.X;
p_y_new = Cursor.Position.Y;


double ratio = p_x_new / p_x;

int he = Convert.ToInt32(100 * ratio);
int we = Convert.ToInt32(100 * ratio);

grafa_1.Clear(Color.White);

for (int i = 0; i < 100; i++)
{
if ((mas[i].width_ != 5555) && (mas[i].height_ != 5555))
{
if (i == n)
{
grafa_1.DrawEllipse(pen_1, mas[i].width_, mas[i].height_, we, he);
}
else
grafa_1.DrawEllipse(pen_1, mas[i].width_, mas[i].height_, 100, 100);
}
}

System.Threading.Thread.Sleep(50);
}
}
}

private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
{
// Мышка отпущена

is_press = false;

//MessageBox.Show("false");
}
}


public class Ellipsoid
{
public int width_;
public int height_;
public Ellipsoid(int r_width, int r_height) { width_ = r_width; height_ = r_height; } // Конструктор
}
}

Ссылка на проект
https://yadi.sk/d/EqpLDIMw3HWz7R

Код

проект целиком
https://yadi.sk/d/EqpLDIMw3HWz7R