Export to PDF in Sharepoint Custom web part.

Question

Hi,
I want to export my page to pdf in sharepoint custm web part. I am using below code to export to pdf. when i click the export button i am getting below
Error. how to resolve this error? pLease help me.
Code
protected void ExporttoPDF_Click(object sender, EventArgs e)
            Response.ContentType = "application/pdf";
            Response.AddHeader("content-disposition", "attachment;filename=ExporttoPDF.pdf");
            Response.Cache.SetCacheability(HttpCacheability.NoCache);
            StringWriter sw = new StringWriter();
            HtmlTextWriter hw = new HtmlTextWriter(sw);
            this.Page.RenderControl(hw);
            StringReader sr = new StringReader(sw.ToString());
            Document pdfDoc = new Document(PageSize.A4, 10f, 10f, 100f, 0f);
            HTMLWorker htmlparser = new HTMLWorker(pdfDoc);
            PdfWriter.GetInstance(pdfDoc, Response.OutputStream);
            pdfDoc.Open();
            htmlparser.Parse(sr);
            pdfDoc.Close();
            Response.Write(pdfDoc);
            Response.End();
Error 
Server Error in '/' Application.
RegisterForEventValidation can only be called during Render();
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.InvalidOperationException: RegisterForEventValidation can only be called during Render();
Source Error:
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack Trace:
[InvalidOperationException: RegisterForEventValidation can only be called during Render();]
   System.Web.UI.ClientScriptManager.RegisterForEventValidation(String uniqueId, String argument) [phone]
   System.Web.UI.WebControls.TextBox.AddAttributesToRender(HtmlTextWriter writer) +455
   System.Web.UI.WebControls.WebControl.RenderBeginTag(HtmlTextWriter writer) +27
   System.Web.UI.WebControls.TextBox.Render(HtmlTextWriter writer) +27
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +240
   System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +42
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +240
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +240
   System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer) +411
   System.Web.UI.HtmlControls.HtmlForm.Render(HtmlTextWriter output) +87
   System.Web.UI.HtmlControls.HtmlForm.RenderControl(HtmlTextWriter writer) +53
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +240
   System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +42
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +240
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +240
   System.Web.UI.Page.Render(HtmlTextWriter writer) +38
   Microsoft.SharePoint.WebPartPages.WikiEditPage.Render(HtmlTextWriter writer) +207
   PayrollProject.PaySlip4Employee.PaySlip4EmployeeUserControl.btnPDF_Click(Object sender, EventArgs e) +425
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +115
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +140
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +29
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2981
Version Information: Microsoft .NET Framework Version:2.0.50727.5472; ASP.NET Version:2.0.50727.5474 

Answer 1

Hi,
We know that the Page.EnableEventValidation property is set to true（The default is true.）,  Sharepoint Custom web(ASP.NET Web) validates that a control event originated from the user interface that was rendered by that control. A control registers its
events during rendering and then validates the events during postback or callback handling.
If you write client script freely,you might have to set "EnableEventValidation = false" in your C# code behind,but this method may be troublesome in SharePoint,
 so the method of "sadomovalex"( http://sadomovalex.blogspot.in/) is a good idea.
Best Regards