C#

private void FrmMain_Shown(object sender, EventArgs epp)
    {
    BackgroundWorker work = new BackgroundWorker();
    work.DoWork += Work_DoWork;
    work.ProgressChanged += Work_ProgressChanged;
    work.RunWorkerCompleted += Work_RunWorkerCompleted;
    work.WorkerReportsProgress = true;
    work.RunWorkerAsync("A parameter of any type you want to pass it");
    }

private void Work_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
    MyTextBox.Text = "Done.";
    }

private void Work_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
    MyTextBox.Text = ($"Progress: {e.ProgressPercentage} - {e.UserState as string}");
    }

private void Work_DoWork(object sender, DoWorkEventArgs e)
    {
    if (sender is BackgroundWorker work)
        {
        for (int i = 0; i < 1000000; i++)
            {
            Thread.Sleep(1000);
            work.ReportProgress(i / 10000, $"An object of any type you want to pass back to the main thread: {i}");
            }
        }
    }

for (int i = 0; i < 1000000; i++) {
   Thread.Sleep(1000);
   work.ReportProgress(i / 10000, $"An object of any type ...: {i}");
}

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows;

using SdPoint = System.Drawing.Point;
using SwPoint = System.Windows.Point;
using SdSize = System.Drawing.Size;
using SwSize = System.Windows.Size;

using GraphicsPath = System.Drawing.Drawing2D.GraphicsPath;
using GReg = System.Drawing.Region;
using GMat2d = System.Drawing.Drawing2D.Matrix;
using GMatMed = System.Windows.Media.Matrix;

namespace GeomLib_August_2021_III
{
    public enum ShapeType
    {
        Line,
        Arc,
        Rectangle,
        Parallelogram,
        Circle,
        Ellipse,
        RegPolygon,
        IrregPolygon,
        Grid,
        Star
    }

    public interface IShape
    {
        string ShpName { get; }
        string ShpComment { get; }
        DateTime ShpTimeStamp { get; }
        ShapeType ShpType { get; }

        Rect SwRect { get; }
        SwPoint CenterF { get; }
        SwPoint[] PathPoints { get; }

        double GetArea();
        double GetPerimeter();
        SwPoint GetCenter();
        GraphicsPath GetGPath();
        Region GetRegion();

        IShape GetUnion(IShape s1, IShape s2);
        IShape GetIntersection(IShape s1, IShape s2);

        IShape Translate(IShape s1, Matrix m1);
        IShape Rotate(IShape s1, Matrix m1);
        IShape Scale(IShape s1, Matrix m1);

        SwPoint[] Flatten();
        void Render();
        void Save();
        void Load()
    }
}

IShape Union(IShape shape);