利用BackgroundWorker 实现线程查询显示进度条,并允许终止查询(模仿SQL查询)

来源：互联网发布：马伯庸三国知乎编辑：程序博客网时间：2024/06/15 13:02

//利用组件实现线程查询
        private SqlCommand fCurCommand;
        private string fCommandText = string.Empty;
        private SqlConnection fConnection;
        private DataSet fdsResult;
        private bool fIsCommandIsCancelOrError = false;

        private delegate void myDelegatDoProcess();
        private delegate void myDelegateSetDataSrc(object t);
        private delegate void PDelegate();
        private delegate void PDelegateA(object t, EventArgs a);

            using (BackgroundWorker backgroundWorker = new BackgroundWorker())
            {
                // 异步获取数据
                backgroundWorker.DoWork += new DoWorkEventHandler(delegate(object o, DoWorkEventArgs workerEventArgs)
                {
                    this.BeginInvoke(new myDelegatDoProcess(doProcess )); //利用委托显示进度条

fCommandText = strSQL;

                    using (SqlDataAdapter fAdapter = new SqlDataAdapter(fCommandText, fConnection ))
                    {
                        try
                        {
                            fIsCommandIsCancelOrError = false;
                            fCurCommand = fAdapter.SelectCommand;
                            fCurCommand.CommandTimeout = 0;// 永不超时
                            fdsResult = new DataSet();
                            fAdapter.Fill(fdsResult);
                            fCurCommand = null;
                        }
                        catch (Exception x)
                        {
                            //MessageBox.Show(x.Message);
                            fIsCommandIsCancelOrError = true; //查询出错或用户已取消查询
                        }
                    }
                });

                // 数据获取完成，绑定数据
                backgroundWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(delegate(object o, RunWorkerCompletedEventArgs x)
                {
                    if (MyGrdQueryResult.IsHandleCreated)
                    {
                        if (!fIsCommandIsCancelOrError)
                        {
                            //this.MyGrdQueryResult.DataSource = fdsResult.Tables[0];
                            bdsQueryResult.DataSource = fdsResult.Tables[0];

this.BeginInvoke(new myDelegateSetDataSrc(SetQueryResultData), new object[] { bdsQueryResult });//显示查询结果集

this.BeginInvoke(new PDelegate(SetGridViewFrmt));//设置列格式

this.BeginInvoke(new PDelegate(ShowCountRecord));//显示记录总数

                            this.BeginInvoke(new PDelegateA(DoExecSumItem), new object[] { null, null });//执行计算合计
                        }
                        if (fIsCommandIsCancelOrError == false)
                        {
                            this.tsPressBarQry.Value = 100;
                        }
                    }
                });

backgroundWorker.RunWorkerAsync();
}

// <summary>
        /// 终止查询
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void tsBtCancel_Click(object sender, EventArgs e)
        {
            if (fCurCommand != null)
            {
                try
                {
                    fCurCommand.Cancel();
                    //MessageBox.Show("查询已停止");
                }
                catch (Exception x)
                {
                    MessageBox.Show(x.Message);
                }
            }
            //flagCancel = true;
            //tmyThrdGetdata.Abort();
            //tmyTrrdProcess.Abort();
        }

/// <summary>
        /// 显示进度条
        /// </summary>
        private void doProcess()
        {
            if (tsPressBarQry.IsDisposed == false)
            {
                this.tsPressBarQry.Value = 0;
                tsPressBarQry.Minimum = 0;
                tsPressBarQry.Maximum = 100;
                tsPressBarQry.Step = 10;
                while ((tsPressBarQry.IsDisposed == false) && (tsPressBarQry.Value < 100))
                {
                    //if (flagCancel) { break; }
                    //if (flagGetDataOver == true) { tsPressBarQry.Value = 100; break; }
                    if (tsPressBarQry.Value == 99)
                    {
                        tsPressBarQry.Value = 0;
                    }
                    tsPressBarQry.Value++;
                    Thread.Sleep(500);
                    Application.DoEvents();
                }
            }
        }