Aps:button onClick event in Visual web part only fires first time - SharePoint 2013

Question

Below is my markup from ascx file
<asp:Button ID="exporttopdf" runat="server" Text="Export To PDF"/>
C# code for button on click
protected void Page_Load(object sender, EventArgs e)
exporttopdf.Click += new System.EventHandler(this.exporttopdf_Click);
protected void exporttopdf_Click(object sender, EventArgs e)
if (Page.IsPostBack)
try
using (MemoryStream stream = new MemoryStream())
PdfPCell cell;
SPList list = SPContext.Current.Site.OpenWeb().Lists[this.ListName];
BaseColor rGBColor = WebColors.GetRGBColor("#AFAECE");
PdfPTable element = new PdfPTable(2)
TotalWidth = 300f,
LockedWidth = true
float[] relativeWidths = new float[] { 1f, 2f };
element.SetWidths(relativeWidths);
element.HorizontalAlignment = Element.ALIGN_MIDDLE;
element.SpacingBefore = 20f;
element.SpacingAfter = 30f;
if (this.PdfHeading != null)
cell = new PdfPCell(new Phrase(this.PdfHeading));
else
cell = new PdfPCell(new Phrase(this.ListName));
cell.Colspan = 2;
cell.Border = 0;
cell.Padding = 4;
cell.BackgroundColor = rGBColor;
cell.HorizontalAlignment = 1;
element.AddCell(cell);
Document document = new Document(PageSize.A4, 25f, 25f, 30f, 30f);
PdfWriter instance = PdfWriter.GetInstance(document, stream);
document.Open();
document.AddAuthor("Place Holder");
document.AddCreator("Place Holder");
document.AddKeywords("Place Holder");
document.AddSubject(this.ListName);
document.AddTitle(this.ListName);
instance.Info.Put(new PdfName("Producer"), new PdfString("Place Holder"));
PdfContentByte directContent = instance.DirectContent;
string[] separator = new string[] { ";", "," };
string[] strArray2 = this.ViewFields.Split(separator, StringSplitOptions.None);
new StringBuilder().Append(this.ListName + "\n");
foreach (string str in strArray2)
PdfPCell cell2 = new PdfPCell(new Phrase(str))
Border = 0,
Padding = 4,
HorizontalAlignment = 1
element.AddCell(cell2);
if (str != "Modified By" && str != "Created By")
PdfPCell cell3 = new PdfPCell(new Phrase(SPContext.Current.Item[str].ToString()))
Border = 0,
Padding = 4,
HorizontalAlignment = 1
element.AddCell(cell3);
else
string[] separatorc = new string[] { "," };
string[] strArray3 = SPContext.Current.Item[str].ToString().Split(separatorc, StringSplitOptions.None);
PdfPCell cell3 = new PdfPCell(new Phrase(strArray3[3].ToString().Substring(8).Replace(@"\\", @"\")))
Border = 0,
Padding = 4,
HorizontalAlignment = 1
element.AddCell(cell3);
PdfPCell cell4 = new PdfPCell(new Phrase("Footer"))
Colspan = 2,
Border = 0,
Padding = 4,
BackgroundColor = rGBColor,
HorizontalAlignment = 1
element.AddCell(cell4);
document.Add(element);
document.Close();
instance.Close();
stream.Close();
HttpContext.Current.Response.Clear();
HttpContext.Current.Response.ContentType = "pdf/application";
string filename = SPContext.Current.Item["Title"].ToString() + ".pdf";
HttpContext.Current.Response.AddHeader("content-disposition", "inline;filename=" + filename);
HttpContext.Current.Response.OutputStream.Write(stream.GetBuffer(), 0, stream.GetBuffer().Length);
HttpContext.Current.Response.End();
catch (Exception exception)
SPDiagnosticsService.Local.WriteTrace(0, new SPDiagnosticsCategory("Export To PDF", TraceSeverity.Unexpected, EventSeverity.Error), TraceSeverity.Unexpected, exception.Message, new object[] { exception.StackTrace });
else
HttpContext.Current.Response.Write("<script language=javascript>alert('ERROR');</script>");
it works fine first time but does not do anything from second.
any advice?

Answer 1

Hi,
Please try to the code snippet as below:
VisualWebPart1.ascx:
<asp:Button ID="exporttopdf" runat="server" Text="Export To PDF" OnClick="exporttopdf_Click"/>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
VisualWebPart1.ascx.cs:
protected void Page_Load(object sender, EventArgs e)
protected void exporttopdf_Click(object sender, EventArgs e)
Label1.Text = System.DateTime.Now.ToString();
If the code still do not work from second, I suggest you debug your code and check whick line of code occur the error.
More information:
http://social.msdn.microsoft.com/Forums/office/en-US/94931a08-f204-4d30-a230-f468815a76e8/export-aspnet-gridview-to-pdf-from-visual-webpart?forum=sharepointdevelopmentprevious
Thanks,
Dennis Guo
TechNet Community Support
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Dennis Guo
TechNet Community Support