Windows窗體嵌入式進度欄后台工作程序

Question

我想在表單中使用進度條，但是遇到了問題。

在加載表單時，進度條完成，並且列表視圖中填充有“已連接”設備的圖標。

當我嘗試在網絡適配器列表中選擇另一個索引時，進度條和列表視圖將清除，但會引發異常，並且GUI中什么也不會發生。

拋出異常：System.Windows.Forms.dll中的“ System.InvalidOperationException”

我假設這是一個線程問題，但我不知道。

這是代碼，非常感謝任何幫助或建議。

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

namespace WindowsFormsApplication1
{
    public partial class ConnectDialog : Form
    {
        BackgroundWorker bkgndWorker = null;
        Dictionary<string, int> dictionary = new Dictionary<string, int>();
        ImageList deviceImageList = new ImageList();

        public ConnectDialog()
        {
            InitializeComponent();       
        }

        public ConnectDialog(List<String> ipAddr)
        {
            InitializeComponent();
            cboNetworkAdapter.Items.AddRange(ipAddr.ToArray());
            cboNetworkAdapter.SelectedIndex = 0;
        }

        private void ConnectDialog_Load(object sender, EventArgs e)
        {
            Bitmap devImage = Properties.Resources.devIcon;
            deviceImageList.Images.Add(devImage);
            deviceImageList.ImageSize = new Size(30, 30);
        }

        private void cboNetworkAdapter_SelectedIndexChanged(object sender, EventArgs e)
        {
            StartWorking();
        }

        private void StartWorking()
        {
            prgBarConnect.Value = 0;
            dictionary.Clear();
            lstvwDevIds.Clear();
            bkgndWorker = new BackgroundWorker();

            bkgndWorker.DoWork += new DoWorkEventHandler(bkgndWorker_DoWork);
            bkgndWorker.ProgressChanged += new ProgressChangedEventHandler(bkgndWorker_ProgressChanged);
            bkgndWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bkgndWorker_RunWorkerCompleted);
            bkgndWorker.WorkerReportsProgress = true;
            bkgndWorker.RunWorkerAsync();
            bkgndWorker.Dispose();
        }

        private void bkgndWorker_DoWork(object sender, DoWorkEventArgs e)
        {
            int numDevs = 0;
            switch (cboNetworkAdapter.SelectedIndex)
            {
                case 0:
                    numDevs = 4;
                    break;
                case 1:
                    numDevs = 1;
                    break;
                case 2:
                    numDevs = 10;
                    break;
            }
            populateImages(numDevs);
        }

        void bkgndWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            prgBarConnect.Value = e.ProgressPercentage;
        }

        void bkgndWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            foreach (KeyValuePair<String, int> entry in dictionary)
            {
                ListViewItem lstViewDevImage = new ListViewItem(entry.Key, entry.Value);
                lstvwDevIds.Items.Add(lstViewDevImage);
            }

            if (lstvwDevIds.SelectedItems.Count > 0)
                Console.WriteLine(String.Format("Device id: {0}", lstvwDevIds.Items.IndexOf(lstvwDevIds.SelectedItems[0])));

            lstvwDevIds.LargeImageList = deviceImageList;
        }

        private void populateImages(int numDevs)
        {
            for (int i = 1; i <= numDevs; i++)
            {
                System.Threading.Thread.Sleep(100);
                int percents = (i * 100) / numDevs;

                String lstVwItemDesc = String.Format("Dev {0}", i - 1);
                dictionary.Add(lstVwItemDesc, deviceImageList.Images.Count - 1);
                bkgndWorker.ReportProgress(percents, i);
            }
        }
    }
}

Answer 1

不要在要運行的BackGroundWorker上調用Dispose。 改為這樣做：

// if we have an instance of a backgroundworker ...
// Cancel and Dispose that one
if (bkgndWorker !=null) 
{
    // in case you want to end the DoWork nicely
    bkgndWorker.CancelAsync(); 
    bkgndWorker.Dispose();
}

// start again
bkgndWorker = new BackgroundWorker();

bkgndWorker.DoWork += new DoWorkEventHandler(bkgndWorker_DoWork);
bkgndWorker.ProgressChanged += new ProgressChangedEventHandler(bkgndWorker_ProgressChanged);
bkgndWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bkgndWorker_RunWorkerCompleted);
bkgndWorker.WorkerReportsProgress = true;
bkgndWorker.RunWorkerAsync();
// removed the call to Dispose

您可能還希望在窗體上實現Dispose ，以對BackgroundWorker實例進行相同的清理。