In this article I will explain with an example, how to resolve the error Unable to cast object of type 'iTextSharp.text.html.simpleparser.CellWrapper' to type 'iTextSharp.text.Paragraph'.
This error occurred, when exporting HTML string to PDF while using HtmlWorker class.
 
 

Solution

The solution for this error is to make use of XmlWorkerHelper class instead of HtmlWorker for converting HTML string to PDF.
 
 

Download iTextSharp and XmlWorkerHelper Libraries

In order to install iTextSharp and XmlWorkerHelper library from Nuget, please refer the following articles.
iTextSharp – Install iTextSharp library using Nuget
XmlWorkerHelper - Install iTextSharp.XmlWorker library using Nuget
 
 

HTML Markup

The following HTML Markup consists of:
GridView – For displaying data.

Columns

There are three BoundField columns for displaying the fields.
Button – For exporting the GridView to PDF file.
The Button has been assigned with a OnClick event handler.
<asp:GridView ID="gvCustomers" runat="server" AutoGenerateColumns="false">
    <Columns>
        <asp:BoundField DataField="Id" HeaderText="Customer Id" ItemStyle-Width="100px" />
        <asp:BoundField DataField="Name" HeaderText="Name" ItemStyle-Width="140px" />
        <asp:BoundField DataField="Country" HeaderText="Country" ItemStyle-Width="120px" />
    </Columns>
</asp:GridView>
<br />
<asp:Button ID="btnExport" runat="server" Text="Export To PDF" OnClick="ExportToPDF" />
 
 

Namespaces

You will need to import the following namespaces.
C#
using System.IO;
using System.Data;
using iTextSharp.text;
using iTextSharp.text.pdf;
using iTextSharp.tool.xml;
 
VB.Net
Imports System.IO
Imports System.Data
Imports iTextSharp.text
Imports iTextSharp.text.pdf
Imports iTextSharp.tool.xml
 
 

Binding the GridView

Inside the Page_Load event handler, the GridView is populated with the records from dynamic DataTable.
Note: For more details on how to create DataTable dynamically and bind to GridView, please refer my article Dynamically create DataTable and bind to GridView in ASP.Net.
 
C#
protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = new DataTable();
        dt.Columns.AddRange(new DataColumn[3] {
            new DataColumn("Id"),
            new DataColumn("Name"),
            new DataColumn("Country")
        });
        dt.Rows.Add(1, "John Hammond", "United States");
        dt.Rows.Add(2, "Mudassar Khan", "India");
        dt.Rows.Add(3, "Suzanne Mathews", "France");
        dt.Rows.Add(4, "Robert Schidner", "Russia");
        gvCustomers.DataSource = dt;
        gvCustomers.DataBind();
    }
}
 
VB.Net
Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim dt As New DataTable()
        dt.Columns.AddRange(New DataColumn(2) {
             New DataColumn("Id"),
             New DataColumn("Name"),
             New DataColumn("Country")
        })
        dt.Rows.Add(1, "John Hammond", "United States")
        dt.Rows.Add(2, "Mudassar Khan", "India")
        dt.Rows.Add(3, "Suzanne Mathews", "France")
        dt.Rows.Add(4, "Robert Schidner", "Russia")
        gvCustomers.DataSource = dt
        gvCustomers.DataBind()
    End If
End Sub
 
 

Exporting GridView to PDF using XmlWorkerHelper class

When Export button is clicked, the PDF is exported.
The StringWriter and HtmlTextWriter class objects are created and the GridView is exported to an HTML string using StringReader class.
Then, the GridView is rendered into an HTML string using RenderControl which accepts HtmlTextWriter class object as parameter.
After that, the generated HTML is added to the iTextSharp PDF document using Document class.
Finally, PDF document is opened and the GridView data is written using ParseXHtml method of XmlWorkerHelper class which converts it to PDF document and the PDF is sent to the Response Stream for download.
C#
protected void ExportToPDF(object sender, EventArgs e)
{
    using (StringWriter sw = new StringWriter())
    {
        using (HtmlTextWriter hw = new HtmlTextWriter(sw))
        {
            gvCustomers.RenderControl(hw);
            StringReader sr = new StringReader(sw.ToString());
            Document pdfDoc = new Document(PageSize.A4, 10f, 10f, 10f, 0f);
            PdfWriter writer = PdfWriter.GetInstance(pdfDoc, Response.OutputStream);
            pdfDoc.Open();
            XMLWorkerHelper.GetInstance().ParseXHtml(writer, pdfDoc, sr);
            pdfDoc.Close();
 
            Response.ContentType = "application/pdf";
            Response.AddHeader("content-disposition", "attachment;filename=GridViewExport.pdf");
            Response.Cache.SetCacheability(HttpCacheability.NoCache);
            Response.Write(pdfDoc);
            Response.End();
        }
    }
}
 
public override void VerifyRenderingInServerForm(Control control)
{
    /* Verifies that the control is rendered */
}
 
VB.Net
Protected Sub ExportToPDF(sender As Object, e As EventArgs)
    Using sw As New StringWriter()
        Using hw As New HtmlTextWriter(sw)
            gvCustomers.RenderControl(hw)
            Dim sr As New StringReader(sw.ToString())
            Dim pdfDoc As New Document(PageSize.A4, 10.0F, 10.0F, 10.0F, 0.0F)
            Dim writer As PdfWriter  = PdfWriter.GetInstance(pdfDoc, Response.OutputStream)
            pdfDoc.Open()
            XMLWorkerHelper.GetInstance().ParseXHtml(writer, pdfDoc, sr)
            pdfDoc.Close()
 
            Response.ContentType = "application/pdf"
            Response.AddHeader("content-disposition", "attachment;filename=GridViewExport.pdf")
            Response.Cache.SetCacheability(HttpCacheability.NoCache)
            Response.Write(pdfDoc)
            Response.End()
        End Using
    End Using
End Sub
 
Public Overrides Sub VerifyRenderingInServerForm(control As Control)
    ' Verifies that the control is rendered
End Sub
 
 

Screenshots

The Form

Unable to cast object of type 'iTextSharp.text.html.simpleparser.CellWrapper' to type 'iTextSharp.text.Paragraph'
 

Exported PDF

Unable to cast object of type 'iTextSharp.text.html.simpleparser.CellWrapper' to type 'iTextSharp.text.Paragraph'
 
 

Demo

View Demo
 
 

Downloads

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