GUI Windows Form C#

using System;
using System.Threading;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
public struct MyData {
    public double pi;
    public int iters;
}
public class Calc {
    private double _pi;
    private int _iters;
    private readonly int TotalIters;
    public Calc(int it) {
        _iters = 1;
        _pi = 0;
        TotalIters = it;
    }
    public MyData PI {
        get {
            MyData pi = new MyData();
            lock (this) {
                pi.pi = _pi;
                pi.iters = _iters;
            }
            return pi;
        }
    }
    public Thread MakeThread() {
        return new Thread(new ThreadStart(this.ThreadStarter));
    }
    private void calculate() {
        double series = 0;
        do {
            series ++;
            lock (this) {
                _iters += 4;
                _pi = series * 4;
            }
        } while (_iters < TotalIters);
    }
    private void ThreadStarter() {
        try {
            calculate();
        } catch (ThreadAbortException e) {
            Console.WriteLine("ThreadAbortException");
        }
    }
}
public class Form1 : System.Windows.Forms.Form {
    private System.Windows.Forms.Label label1;
    private System.Windows.Forms.TextBox PiValue;
    private System.Windows.Forms.Label label2;
    private System.Windows.Forms.TextBox Iteratons;
    private Calc pi = new Calc(100000000);
    private Thread calcThread = null;
    private System.Windows.Forms.Timer timer1;
    private System.Windows.Forms.Button StopButton;
    private System.Windows.Forms.Button Pause;
    private System.ComponentModel.IContainer components;
    public Form1() {
        this.label1 = new System.Windows.Forms.Label();
        this.label2 = new System.Windows.Forms.Label();
        this.Pause = new System.Windows.Forms.Button();
        this.PiValue = new System.Windows.Forms.TextBox();
        this.StopButton = new System.Windows.Forms.Button();
        this.timer1 = new System.Windows.Forms.Timer(this.components);
        this.Iteratons = new System.Windows.Forms.TextBox();
        this.SuspendLayout();
        // 
        // label1
        // 
        this.label1.Location = new System.Drawing.Point(8, 24);
        this.label1.Name = "label1";
        this.label1.TabIndex = 0;
        this.label1.Text = "Value  of PI:";
        // 
        // label2
        // 
        this.label2.Location = new System.Drawing.Point(8, 72);
        this.label2.Name = "label2";
        this.label2.TabIndex = 2;
        this.label2.Text = "Iterations:";
        // 
        // Pause
        // 
        this.Pause.Location = new System.Drawing.Point(24, 112);
        this.Pause.Name = "Pause";
        this.Pause.TabIndex = 5;
        this.Pause.Text = "Pause";
        this.Pause.Click += new System.EventHandler(this.Pause_Click);
        // 
        // PiValue
        // 
        this.PiValue.Location = new System.Drawing.Point(128, 24);
        this.PiValue.Name = "PiValue";
        this.PiValue.ReadOnly = true;
        this.PiValue.Size = new System.Drawing.Size(136, 20);
        this.PiValue.TabIndex = 1;
        this.PiValue.Text = "";
        // 
        // StopButton
        // 
        this.StopButton.Location = new System.Drawing.Point(200, 112);
        this.StopButton.Name = "StopButton";
        this.StopButton.TabIndex = 4;
        this.StopButton.Text = "Stop";
        this.StopButton.Click += new System.EventHandler(this.StopButton_Click);
        // 
        this.timer1.Enabled = true;
        this.timer1.Tick += new System.EventHandler(this.timer1_Tick);
        // 
        this.Iteratons.Location = new System.Drawing.Point(128, 72);
        this.Iteratons.Name = "Iteratons";
        this.Iteratons.ReadOnly = true;
        this.Iteratons.TabIndex = 3;
        this.Iteratons.Text = "";
        // 
        this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
        this.ClientSize = new System.Drawing.Size(292, 149);
        this.Controls.AddRange(new System.Windows.Forms.Control[]  {
                                                                  this.Pause,
                                                                  this.StopButton,
                                                                  this.Iteratons,
                                                                  this.label2,
                                                                  this.PiValue,
                                                                  this.label1});
        this.Load += new System.EventHandler(this.Form1_Load);
        this.Closed += new System.EventHandler(this.Form1_Closed);
        this.ResumeLayout(false);
    }
    [STAThread]
    static void Main() {
        Application.Run(new Form1());
    }
    private void Form1_Load(object sender, System.EventArgs e) {
        calcThread = pi.MakeThread();
        calcThread.Priority = ThreadPriority.Lowest;
        calcThread.Start();
    }
    private void timer1_Tick(object sender, System.EventArgs e) {
        if (this.Pause.Text == "Pause") {
            MyData p = pi.PI;
            this.PiValue.Text = p.pi.ToString();
            this.Iteratons.Text = p.iters.ToString();
        }
        if (calcThread.IsAlive == false) {
            StopButton.Enabled = false;
            Pause.Enabled = false;
            timer1.Enabled = false;
            calcThread = null;
        }
    }
    private void StopButton_Click(object sender, System.EventArgs e) {
        StopButton.Enabled = false;
        Pause.Enabled = false;
        timer1.Enabled = false;
        calcThread.Abort();
        calcThread.Join();
        calcThread = null;
    }
    private void Pause_Click(object sender, System.EventArgs e) {
        if (this.Pause.Text == "Pause") {
            calcThread.Suspend();
            this.Pause.Text = "Resume";
            this.StopButton.Enabled = false;
        } else {
            calcThread.Resume();
            this.Pause.Text = "Pause";
            this.StopButton.Enabled = true;
        }
    }
    private void Form1_Closed(object sender, System.EventArgs e) {
        if (calcThread != null) {
            calcThread.Abort();
            calcThread.Join();
        }
    }
}