WinForm 进度条

目标：MyForm上有个Button，按下后会执行Task，Task会返回中间结果，然后在Label上实时显示中间结果。

using System;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

public partial class MyForm : Form
{

    //1)Label的更新
    private readonly object statusLabel = new object();
    private void UpdateLabel(string txt)
    {
        lock (statusLabel)
        {
            this.Label1.Text = txt;
        }
    }

    //2)Task定义
    Random rand = new Random();
    public void SearchFilesInTarget(IProgress<string> onSearchingFile) 
    {
        while (true)
        {
            string result = "file_name" + rand.Next();
            onSearchingFile.Report(result);
        }
    }

    //3)按钮按下
    private readonly CancellationTokenSource cancelToken = new CancellationTokenSource();
    private void SearchStart_Click(object sender, EventArgs e)
    {
        var onSearchingFile = new Progress<string>(txt => this.BeginInvoke(updateLabel, "Searching..." + txt));
        Task myTask = Task.Factory.StartNew(() => SearchFilesInTarget(onSearchingFile), cancelToken.Token);
    }


    //4)构造BeginInvoke的参数
    public delegate void DelegateUpdateLabel(string file);
    private DelegateUpdateLabel updateLabel;

    public MyForm()
    {
        updateLabel = new DelegateUpdateLabel(UpdateLabel);
    }
}