[DotNetDevelopment] cross thread operation not valid

[Dickery1]

i get a error cross thread operation not valid when it is trying to
write to the textfield.
 void appendToTextBox(string str){


i have a feeling that the delegates run in a different thread and when
the events are triggered, they are trying to write to the form thread.
i guess C# does not like it. how do i fix it.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using Krs.Ats.IBNet;

using Krs.Ats.IBNet.Contracts;

namespace collectTickData
{
    public partial class Form1 : Form
    {
        private static IBClient client;

        public Form1()
        {
            InitializeComponent();
        }
        private   void appendToTextBox(string str){
            textBox1.Text  += str + "\r\n";

        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            client = new IBClient();
            client.ThrowExceptions = true;
            client.Error += client_Error;
            client.TickPrice += client_TickPrice;
            client.TickSize += client_TickSize;
            Console.WriteLine("Connecting to IB.");
            client.Connect(textBox1.Text, Int32.Parse(textBox2.Text),
10);
            //Forex Test
            Forex EUR = new Forex("EUR", "USD");
            client.RequestMarketData(17, EUR, null, false);

        }
        void client_TickSize(object sender, TickSizeEventArgs e)
        {
           appendToTextBox("Tick Size: " + e.Size + " Tick Type: " +
EnumDescConverter.GetEnumDescription(e.TickType));
        }

         void client_Error(object sender, ErrorEventArgs e)
        {
            appendToTextBox("Error: " + e.ErrorMsg);
        }

         void client_TickPrice(object sender, TickPriceEventArgs e)
        {
            appendToTextBox("Price: " + e.Price + " Tick Type: " +
EnumDescConverter.GetEnumDescription(e.TickType));
        }


    }
}