Why does form freeze?

This program is writing numbers from 1 to 5000 in thread, but main form freezes anyway. Where is an error? Tha开发者_开发知识库nks in advance.

Code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.IO;
using System.Threading;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        int how, current;
        bool job;
        Object lockobj = new Object();

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            MessageBox.Show("Started!");
            how = 5000;
            current = 0;
            job = true;
            Thread worker = new Thread(Go);
            worker.Name = "1";
            worker.Start();
        }

        private void Go()
        {
            while (job)
            {
                if (current < how)
                {

                    lock (lockobj)
                    {
                        current++;
                    }

                    log(string.Format("Thread #{0}: {1}", Thread.CurrentThread.Name, current));
                }
                else
                {
                    job = false;
                }
            }
        }


        private void log(string text)
        {
            Action A = new Action(() =>
            {
                richTextBox1.AppendText(text + System.Environment.NewLine);
            });

            if (richTextBox1.InvokeRequired)
                this.BeginInvoke(A);
            else A();
        }
    }


}

Because most of your work will be spent in

        if (richTextBox1.InvokeRequired)
            this.BeginInvoke(A);

and while you invoke the form it is locked.

Do some real work, like Thread.Sleep(1000); :-) , instead of current++; and your form will be response between the updates.

It freezes because you are rendering on the textbox very quickly and the GUI doesn't have time to keep in sync. Remember that this rendering happens on the main GUI thread and by calling BeginInvoke to update the textbox so rapidly actually consumes all the resources of this main GUI thread. Try lowering the frequency at which you are logging to avoid this behavior.