Question

我的应用程序运行一些可能需要很长时间的数据库查询。

执行这些查询时，我的应用程序似乎冻结，看起来应用程序已停止工作。

我需要使用进度条来避免此问题，但我不确定如何预测查询执行所需的时间。

运行查询的代码位于

之下

private void CheckSsMissingDate()
 {
  while (DateTime.Parse(time) <= DateTime.Now)
   {
     var ssCon = OpenSQLConnection();
     var cmd = new SqlCommand("SELECT TOP (1)Date_Time,Value1,Value2,Value3,Value4,Value5,Value6,
         "+ "Value7,Value8,Value9 from RAW_S001T01 where Date_Time >='" + tempTime + "'",ssCon);
     var dr = cmd.ExecuteReader();
     var count = 0;
     while (dr.Read())
      {
        ssChkDate = (dr["Date_Time"].ToString());
        conssChkDate = DateTime.Parse(ssChkDate).ToString("yyyy-MM-dd HH:mm:ss");
        tempTime = Convert.ToDateTime(ssChkDate);
        tempTime = tempTime.AddMinutes(15);
        TValue1 = (dr["Value1"].ToString());
        TValue2 = (dr["Value2"].ToString());
        TValue3 = (dr["Value3"].ToString());
        TValue4 = (dr["Value4"].ToString());
        TValue5 = (dr["Value5"].ToString());
        TValue6 = (dr["Value6"].ToString());
        TValue7 = (dr["Value7"].ToString());
        TValue8 = (dr["Value8"].ToString());
        TValue9 = (dr["Value9"].ToString());
        if (CheckMsMissingDate(conssChkDate) == false)
          {
            InsertMissing(conssChkDate,TValue1,TValue2,TValue3,TValue4,TValue5,TValue6,TValue7,TValue8,TValue9);
                    count = count + 1;
           }
        }
       dr.Close();
       ssCon.Close();
       updateCount.Text = count + @" Missing Records added.";
    }
}

如何显示进度条以显示查询的进度？

Answer 1

您可以使用BackgroundWorker()来解决此类问题。

首先定义类BackgroundWorker()的全局变量喜欢

private BackgroundWorker bgw;

然后在开始执行查询时使用下面的代码，例如button1_Click()事件或其他任何内容。

bgw = new BackgroundWorker();
bgw.WorkerReportsProgress = true;
bgw.ProgressChanged += new ProgressChangedEventHandler(bgw_ProgressChanged);
bgw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bgw_RunWorkerCompleted);
bgw.DoWork += new DoWorkEventHandler(bgw_DoWork);
bgw.RunWorkerAsync();

现在定义如下方法：

void bgw_DoWork(object sender, DoWorkEventArgs e)
 {
  //Your time taking work. Here it's your data query method.
  CheckSsMissingDate();
 }

void bgw_ProgressChanged(object sender, ProgressChangedEventArgs e)
 {
   //Progress bar.
   progressBar1.Value = e.ProgressPercentage;
 }

 void bgw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
  {
   //After completing the job.
   MessageBox.Show(@"Finished");
  }

Answer 2

如果您不希望应用程序冻结，则应使用最近在C＃中实现的async / await关键字，或者您可以手动编写异步代码。

参考：MSDN

C＃中长时间运行任务的进度条

2 个答案: