This is a basic multithreading template which demonstrates how to update your UI from a non UI thread

MultithreadingTemplate.cs

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Shown(object sender, EventArgs e)
        {
            void updateUI()
            {
                UpdateResponse();
            }
            new Thread(updateUI).Start();
        }
        public delegate void Callback(string text);
        private void UpdateResponse()
        {
            StringBuilder sb = new StringBuilder();
            sb.Append("My message");
            Invoke(new Callback(UpdateMethod), new object[] { (sb.ToString()) });
        }
        private void UpdateMethod(string responsiveMsg)
        {
            textBox1.Text = responsiveMsg;
        }
    }