c# - 单击按钮时中止正在运行的功能

Question

我有一个网页有一个功能，当我们点击 pdf 时，它会随时获取打印机的值。这需要一些时间，因此在反复点击时，网页会崩溃。

有什么方法可以中止当前正在运行的函数，或者可以以某种方式在单击后禁用按钮单击？

界面代码:

 <asp:UpdatePanel ID="UpdatePanel2" runat="server">
    <Triggers>
 <asp:PostBackTrigger ControlID="imgExportPDF" />
    </Triggers>
<ContentTemplate>
        <table id="topHeading" width="100%" cellspacing="0" cellpadding="0" border="0" class="PageHeader">
            <tr align="center" style="height: 25px" class="PageHeader2">
                <td>
                    &nbsp;
                </td>
                <td align="right" valign="bottom" style="width: 30%" visible="false">
                <asp:ImageButton ID="imgExportPDF" runat="server" ImageUrl="~/Images/pdf-Export.jpg"

                </td>
            </tr>
        </table>
    </ContentTemplate>
</asp:UpdatePanel>

还有我的后端代码:

protected void imgExportPDF_Click(object sender, ImageClickEventArgs e)
{

    saveDetails();

    int counterAdd = 0;

    DataSet dsDevNotReady = CDBIntract.GetDevNotReady(EnterpriseV, CDInfonew.Count);
    if (dsDevNotReady != null)
    {
        if (dsDevNotReady.Tables[0].Rows.Count > 0)
        {
            for (int i = 0; i < dsDevNotReady.Tables[0].Rows.Count; i++)
            {
                sb.Append((deviceCounter + 1) + ". IP Address : " + dsDevNotReady.Tables[0].Rows[i]["IPAddress"].ToString() + "  And Model Name : " + dsDevNotReady.Tables[0].Rows[i]["Model"].ToString() + "  On Date : " + DateTime.Now.ToString() + " " + dsDevNotReady.Tables[0].Rows[i]["Info"].ToString());
                sb.Append("\r\n");
                deviceCounter++;
            }
            counterAdd++;
        }
    }

    int countData = 0;
    DataSet dsdev= CDBIntract.Blah(EnterpriseV, CDInfonew.Count);

    if (dsDev != null)
    {

        if (dsDev.Tables[0].Rows.Count > 0)
        {
            countData = dsDev.Tables[0].Rows.Count + Convert.ToInt32(dsDev.Tables[1].Rows[0]["AditionalRows1"].ToString()) + Convert.ToInt32(dsDev.Tables[2].Rows[0]["AditionalRows2"].ToString());
            PdfDocument myPdfDocument = new PdfDocument(PdfDocumentFormat.A4);
            PdfTable myPdfTable = myPdfDocument.NewTable(new Font("Verdana", 8), countData + counterAdd, 2, 4);
            myPdfTable.ImportDataTable(returnTable(dsDev, deviceCounter, sb.ToString()));

            //Set PDF Table Style
            myPdfTable.HeadersRow.SetFont(new Font("Arial", 8, FontStyle.Bold));
            myPdfTable.HeadersRow.SetColors(System.Drawing.Color.Gray, System.Drawing.Color.Gray);
            myPdfTable.SetColors(Color.Black, Color.White, Color.White);
            myPdfTable.SetBorders(Color.Gray, 1, BorderType.CompleteGrid);

            myPdfTable.SetColumnsWidth(new int[] { 30, 30 });
            int[] arrayDevice = listDevice.ToArray();
            for (int m = 0; m < arrayDevice.Length; m++)
            {
                try
                {
                    foreach (PdfCell pc in myPdfTable.CellRange(arrayDevice[m], 0, arrayDevice[m], 0).Cells)
                    {
                        pc.ColSpan = 2;
                        pc.SetCellPadding(4);
                        pc.SetColors(Color.Red, Color.LightGray);
                        pc.SetFont(new Font("Arial", 10, FontStyle.Bold));
                    }
                }
                catch (Exception ex)
                { }
            }
            int[] array = list.ToArray();
            for (int m = 0; m < array.Length; m++)
            {
                try
                {
                    foreach (PdfCell pc in myPdfTable.CellRange(array[m], 0, array[m], 0).Cells)//(0//,0//,0//Number of rows,0//column)
                    {
                        pc.ColSpan = 2;
                        pc.SetCellPadding(4);
                        pc.SetColors(Color.Blue, Color.LightGray);
                        pc.SetFont(new Font("Arial", 10, FontStyle.Bold));
                    }
                }
                catch (Exception ex)
                { }
            }
            int[] array1 = list2.ToArray();
            for (int n = 0; n < array1.Length; n++)
            {
                try
                {
                    foreach (PdfCell pc in myPdfTable.CellRange(array1[n], 0, array1[n], 0).Cells)//(0//,0//,0//Number of rows,0//column)
                    {
                        pc.ColSpan = 2;
                        pc.SetCellPadding(4);
                        pc.SetColors(Color.Blue, Color.LightGray);
                        pc.SetFont(new Font("Arial", 8, FontStyle.Bold));
                    }
                }
                catch (Exception ex)
                { }
            }
            int[] array2 = list3.ToArray();
            for (int k = 0; k < array2.Length; k++)
            {
                try
                {

                    foreach (PdfCell pc in myPdfTable.CellRange(array2[k], 0, array2[k], 0).Cells)//(0//,0//,0//Number of rows,0//column)
                    {
                        pc.ColSpan = 2;
                        pc.SetCellPadding(4);
                        //pc.SetColors(Color.Blue, Color.LightGray);
                        if (k == 0)
                            pc.SetFont(new Font("Arial", 8, FontStyle.Bold));
                    }
                }
                catch (Exception ex)
                {
                }
            }
            myPdfTable.SetRowHeight(100);
            // Now we set some alignment... for the whole table and then, for a column.
            myPdfTable.SetContentAlignment(ContentAlignment.MiddleLeft);

            string logo = HttpContext.Current.Server.MapPath(".") + "/images/Printeaze_Logo02.jpg";
            PdfImage LogoImage = myPdfDocument.NewImage(logo);

            string companylogo = HttpContext.Current.Server.MapPath(".") + "/images/CompanyLogo.jpg";
            PdfImage CompanyLogo = myPdfDocument.NewImage(companylogo);

            int i = 0;
            PdfTablePage newPdfTablePage;

            // Here we start the loop to generate the table...
            while (!myPdfTable.AllTablePagesCreated)
            {
                // we create a new page to put the generation of the new TablePage:
                i++;

                PdfPage newPdfPage = myPdfDocument.NewPage();

                if (i == 1)
                {

                    newPdfTablePage =
                        myPdfTable.CreateTablePage(new PdfArea(myPdfDocument, 18, 120, 560, 680));
                    // newPdfTablePage =
                    //     myPdfTable.CreateTablePage(new PdfArea(myPdfDocument, 18, 120, 560, 450));

                    newPdfPage.Add(LogoImage, 460, 30, 120);
                    newPdfPage.Add(CompanyLogo, 20, 20, 120);
                    // we also put a Label 
                    PdfTextArea pta = new PdfTextArea(new Font("Verdana", 16, FontStyle.Bold), Color.Black
                        , new PdfArea(myPdfDocument, 20, 70, 350, 20), ContentAlignment.MiddleLeft, "Blah");

                    newPdfPage.Add(newPdfTablePage);
                    newPdfPage.Add(pta);
                    //PointF pointstart = new PointF(20, 140);
                    //PointF pointend = new PointF(578, 140);
                }
                else
                {
                    newPdfTablePage = myPdfTable.CreateTablePage(new PdfArea(myPdfDocument, 18, 15, 560, 800));
                    // newPdfTablePage = myPdfTable.CreateTablePage(new PdfArea(myPdfDocument, 18, 15, 600, 650));
                    newPdfPage.Add(newPdfTablePage);
                }

                newPdfPage.SaveToDocument();
            }
            // Finally we save the docuement...
            //myPdfDocument.SaveToFile("PDF.pdf");
            MemoryStream stream = new MemoryStream();
            myPdfDocument.SaveToStream(stream);
            Response.ClearHeaders();
            Response.ClearContent();
            Response.ContentType = "application/pdf";
            Response.AddHeader("content-disposition", "attachment; filename= Blah.pdf");
            Response.BinaryWrite(stream.ToArray());
            HttpContext.Current.ApplicationInstance.CompleteRequest();
        }
    }
}

Answer 1

单击按钮时使用 JavaScript 禁用该按钮。

如果这还不够，您需要在代码隐藏中跟踪(存储在静态列表或其他内容中)用户 session ，并检查特定 session 是否已开始但尚未完成 PDF 调用，然后简单地退出重复项如果第一个未完成，则调用。

HttpContext.Current.Session

这将需要各种安全防护措施，这会增加复杂性，以防止用户在出现错误时完全无法生成 PDF。