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public class WebHttp
{
    /// <summary>
    /// get请求带重试
    /// </summary>
    /// <param name="Url"></param>
    /// <param name="postDataStr"></param>
    /// <param name="sum"></param>
    /// <returns></returns>
    public static string HttpGet(string Url, string postDataStr, int sum)
    {
        string temp=null;
        for (int i = 0; i < sum; i++)
        {
            if (string.IsNullOrEmpty(temp) || string.IsNullOrEmpty(temp.Trim()))
            {
                temp = HttpGet(Url, postDataStr);
            }
            else {
                break;
            }
        }
        return temp;
    }
    /// <summary>
    /// post请求带重试
    /// </summary>
    /// <param name="Url"></param>
    /// <param name="postDataStr"></param>
    /// <param name="sum"></param>
    /// <returns></returns>
    public static string HttpPost(string Url, string postDataStr, int sum)
    {
        string temp = null;
        for (int i = 0; i < sum; i++)
        {
            if (string.IsNullOrEmpty(temp) || string.IsNullOrEmpty(temp.Trim()))
            {
                temp = HttpPost(Url, postDataStr);
            }
            else
            {
                break;
            }
        }
        return temp;
    }
    /// <summary>
    /// GET请求与获取结果
    /// </summary>
    public static string HttpGet(string Url, string postDataStr)
    {
        try
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url + (postDataStr == "" ? "" : "?") + postDataStr);
            request.Method = "GET";
            request.ContentType = "text/html;charset=UTF-8";
            request.Timeout = 10000;
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            Stream myResponseStream = response.GetResponseStream();
            StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.UTF8);
            string retString = myStreamReader.ReadToEnd();
            myStreamReader.Close();
            myResponseStream.Close();
            return retString;
        }
        catch (Exception ex)
        {
            return null;
        }
    }
    /// <summary>
    /// POST请求与获取结果
    /// </summary>
    public static string HttpPost(string Url, string postDataStr)
    {
        try
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
            request.Method = "POST";
            request.Timeout = 6000000;
            request.ContentType = "application/x-www-form-urlencoded";
            request.ContentLength = postDataStr.Length;
            StreamWriter writer = new StreamWriter(request.GetRequestStream(), Encoding.ASCII);
            writer.Write(postDataStr);
            writer.Flush();
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            string encoding = response.ContentEncoding;
            if (encoding == null || encoding.Length < 1)
            {
                encoding = "UTF-8"; //默认编码
            }
            StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding(encoding));
            string retString = reader.ReadToEnd();
            return retString;
        }
        catch (Exception ex)
        {
            return null;
        }
    }
}

using System;
using System.ComponentModel;
using System.Windows.Forms;
 
namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        private BackgroundWorker bgWorker = new BackgroundWorker();
 
        public Form1()
        {
            InitializeComponent();
            InitializeBackgroundWorker();
        }
 
        private void InitializeBackgroundWorker()
        {
            bgWorker.WorkerReportsProgress = true;
            bgWorker.WorkerSupportsCancellation = true;
            bgWorker.DoWork += new DoWorkEventHandler(bgWorker_DoWork);
            bgWorker.ProgressChanged += new ProgressChangedEventHandler(bgWorker_ProgessChanged);
            bgWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bgWorker_WorkerCompleted);
        }
 
   
        public void bgWorker_DoWork(object sender, DoWorkEventArgs e)
        {
            for (int i = 0; i <= 100; i++)
            {
                if (bgWorker.CancellationPending)
                {
                    e.Cancel = true;
                    return;
                }
                else
                {
                    bgWorker.ReportProgress(i, "Working");
                    System.Threading.Thread.Sleep(10);
                }
            }
        }
 
        public void bgWorker_ProgessChanged(object sender, ProgressChangedEventArgs e)
        {
            string state =(string)e.UserState;//接收ReportProgress方法传递过来的userState
            this.label2.Text = "状态:" +state;
            this.progressBar1.Value = e.ProgressPercentage;
            this.label1.Text = "处理进度:" + Convert.ToString(e.ProgressPercentage) + "%";
        }
 
        public void bgWorker_WorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Error != null)
            {
                MessageBox.Show(e.Error.ToString());
                return;
            }
            if (!e.Cancelled)
                this.label1.Text = "处理完毕!";
            else
                this.label1.Text = "处理终止!";
 
        }
     
        private void btnStart_Click_1(object sender, EventArgs e)
        {
            if (bgWorker.IsBusy)
                return;
            this.progressBar1.Maximum = 100;
            this.btnStart.Enabled = false;
            this.btnStop.Enabled = true;
            bgWorker.RunWorkerAsync("hello");
        }
 
        private void btnStop_Click_1(object sender, EventArgs e)
        {
            this.btnStart.Enabled = true;
            this.btnStop.Enabled = false;
            bgWorker.CancelAsync();
        }
    }
}

方法一

var obj={}
if(Object.values(obj).length>0){
    // 有值  
}else{
  // 无
}

方法二

//封装为一个方法判断变量是否为空
    isobjEmpty(obj) {
      if (obj === null || obj === undefined || obj === "" || obj.length === 0 || obj === {}) {
        return true;
      } else {
        return false;
      }
    },
    //使用
    if(!this.isobjEmpty(obj)){
        //存在
    }else{
        //不存在
    }

                        if (jo.Property("abc") != null)
                        {

                        }