backgroundWorker

worker.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Security;
using WordAddIn1.Tool;
using WordAddIn1.Model;
using System.IO;
using System.Net.Http;
using System.Net.Http.Headers;
using Flurl.Http;
using RestSharp;

namespace WordAddIn1
{
    public partial class UploadPage : UserControl
    {
        private delegate void HttpDoneDelegate(string text);
        private static readonly HttpClient client = new HttpClient();
       
        public UploadPage()
        {
            InitializeComponent();
            progressBar1.Visible = false;
        }
        private void button2_ClickAsync(object sender, EventArgs e)
        {
            progressBar1.Visible = true;

            var bw = new BackgroundWorker();
            bw.DoWork += new DoWorkEventHandler(get);
            bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(get_done);
            bw.RunWorkerAsync();
            

        }
        private void get(object sender, DoWorkEventArgs e)
        {

            var client = new RestClient("https://slack.com/api/");
            var request = new RestRequest("api.test", Method.GET);
            IRestResponse response = client.Execute(request);
            var content = response.Content; // raw content as string
            Console.Write(content);
            BackgroundWorker worker = sender as BackgroundWorker;
            e.Result = content;

        }
        private void get_done(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Cancelled)
            {
                return;
            }
            if(e.Error != null)
            {
                MessageBox.Show(e.Error.Message);
                return;
            }
            var result = e.Result as string;
            //way1:
            //progressBar1.Invoke((MethodInvoker)(() =>
            //      GetResult(result)
            //));
           
           //way2
            HttpDoneDelegate dele1 = new HttpDoneDelegate(GetResult);
            this.BeginInvoke(dele1,new object[] { result});
            
        }
        private void GetResult(string text)
        {
            button2.Text = text;
            progressBar1.Visible = false;
         }
    }
   
}