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用BackgroundWorder 加 progressbar 常用于在頁面長時間處理事件中顯示進度條. 

WorderReportProgress \ WorkerSupportCancellation 屬性設置為True.

1、调用BackgroundWorker的RunWorkerAsync方法(可以传递参数)，它将调用DoWork事件

2、在DoWork的事件响应代码中调用耗时的操作. 3、在耗时操作中判断CancellationPending属性，如果为false则退出 4、如果要向用户界面发送信息，则调用BackgroundWorker的ReportProgress方法，它将调用ProgressChanged事件(可以将改变通过object类型传递) 5、在ProgressChanged事件的响应代码中将改变呈现给用户 6、如果需要取消耗时操作，则调用BackgroundWorker的CancelAsync方法，需要和步骤3一起使用

例如:

/// 
        /// do work event. 耗時事件        /// 
        ///         ///         private void bgWorker_DoWork(object sender, DoWorkEventArgs e)        {            //export to excel            string[] tableName = { "WI", "WI_Details" };            exporttoexcel.ExportExcel(ds, false, this.bgw, tableName);               //  frmMain.form1.bgWorker.ReportProgress(percent);  //在耗時事件ExportExcel 中間,報告進度,這時會調用   bgWorker_ProgressChanged事件                }        /// 
        /// 耗時事件中進度條變化        /// 
        ///         ///         public void bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)        {                      pgBar.Value = e.ProgressPercentage;          }        /// 
        /// 耗時事件完成后        /// 
        ///         ///         private void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)        {            bgWorker.Dispose();            pgBar.Value = 0;            pgBar.Visible = false;                              }//-------------------------------------------------    class ExportToExcel{              /// 
        /// export the dataset to excel        /// 
        /// the dataset will be exported to excel        /// set the odd and event rows have different color.         /// the name of BackgroundWorker.  yes        /// sheets 's name         ///         public void ExportExcel(DataSet ds, bool oddEvenColor, object bgWorker,string[] tableName)    {               if (ds == null || ds.Tables .Count == 0) return;        try        {            Microsoft.Office.Interop.Excel.Application xlApp = new Microsoft.Office.Interop.Excel.Application();            if (xlApp == null)            {                return;            }            System.Globalization.CultureInfo CurrentCI = System.Threading.Thread.CurrentThread.CurrentCulture;            System.Threading.Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo("en-US");            Microsoft.Office.Interop.Excel.Workbooks workbooks = xlApp.Workbooks;                    Microsoft.Office.Interop.Excel.Workbook workbook = workbooks.Add();                int rowRead = 0;                int rowCount = 0;                //get the table's rows count                foreach (DataTable dt in ds.Tables)                {                    rowCount += dt.Rows.Count;                }                               for (int tbi = 0; tbi < ds.Tables.Count; tbi++)                {                                    Microsoft.Office.Interop.Excel.Worksheet worksheet = (Microsoft.Office.Interop.Excel.Worksheet) workbook.Worksheets.Add();                    worksheet.Name = tableName[tbi].ToString();                    if (worksheet == null)//工作薄中没有工作表                    {                        return;                    }                    Microsoft.Office.Interop.Excel.Range range;                          int percent = 0;                    //title column name                    for (int i = 0; i < ds.Tables[tbi].Columns.Count; i++)                    {                        worksheet.Cells[1, i + 1] = ds.Tables[tbi].Columns[i].ColumnName;                        range = (Microsoft.Office.Interop.Excel.Range)worksheet.Cells[1, i + 1];                        range.Interior.ColorIndex = 31;                        range.Font.Size = 12;                        range.Font.Bold = true;                        range.Borders.LineStyle = 1;                        range.Font.ColorIndex = 2;//white                     }                    //content                                    for (int r = 0; r < ds.Tables[tbi].Rows.Count; r++)                    {                        if (bgWorker != null && (bgWorker as BackgroundWorker).CancellationPending)                            //if (frmMain.form1.bgWorker.CancellationPending)//如果有取消則退出導出                                                    break;                        for (int i = 0; i < ds.Tables[tbi].Columns.Count; i++)                        {                            worksheet.Cells[r + 2, i + 1] = ds.Tables[tbi].Rows[r][i].ToString();                                                    }                        rowRead++;                        percent = ((int)(100 * rowRead)) / rowCount;                        if (bgWorker != null && percent <= 100)                        {                            (bgWorker as BackgroundWorker).ReportProgress(percent);                            //frmMain.form1.bgWorker.ReportProgress(percent);                                                }                    }　  range = worksheet.Range(worksheet.Cells［2, 1］, worksheet.Cells［ds.Tables［tbi］.Rows.Count + 1, ds.Tables［tbi］.Columns.Count］)                            range.Borders.LineStyle = 1;                            if (oddEvenColor)                            {                                if (r % 2 == 1)                                    range.Interior.ColorIndex = 34;//隔行換底色                            }                            range.Font.Size = 9;                    worksheet.Columns.AutoFit(); //列寬自適應                }            xlApp.Visible = true;        }        catch (Exception e)        {            throw (e);        }    }

 

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