Getting System.NullReferenceException Error While Creating PDF Files

Question

User-1062969975 posted

Hello guys,

I need some suggestions from any one that who can help me to solve my problem.

I have created aspx with itextsharp and it works if I right click and open with browser. I can fill the forms which include textboxes and radiabuttonlists and press the print button to create PDF.

But when I try to run project it gave System.NullReferenceException error at this point 

Dim writer = PdfWriter.GetInstance(doc, output)

Here is my aspx.vb codes

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        If TextBox1.Text = "" Then
            MsgBox("Lütfen Rapor Numarasını Giriniz", Title:="Teknik Servis Raporları")
        ElseIf TextBox2.Text = "" Then
            MsgBox("Lütfen Rapor Tarihini Giriniz", Title:="Teknik Servis Raporları")
        ElseIf TextBox3.Text = "" Then
            MsgBox("Lütfen Kurum Adını Giriniz", Title:="Teknik Servis Raporları")
        ElseIf TextBox4.Text = "" Then
            MsgBox("Lütfen Cihaz Markasını Giriniz", Title:="Teknik Servis Raporları")
        ElseIf TextBox5.Text = "" Then
            MsgBox("Lütfen Cihaz Modelini Giriniz", Title:="Teknik Servis Raporları")
        ElseIf TextBox6.Text = "" Then
            MsgBox("Lütfen Seri Numarasını Giriniz", Title:="Teknik Servis Raporları")
        Else
 
            Using output = New MemoryStream()
                Dim doc = New Document(PageSize.A4, 1, 1, 10, 10)
                Dim writer = PdfWriter.GetInstance(doc, output)
                writer.CloseStream = False
                doc.Open()
                doc.NewPage()
                Dim Helvetica = itextsharp.text.pdf.BaseFont.CreateFont("Helvetica", "CP1254", itextsharp.text.pdf.BaseFont.NOT_EMBEDDED)
                Dim t1 = New itextsharp.text.Font(Helvetica, 20, PdfFontStyle.Bold)
                Dim t2 = New itextsharp.text.Font(Helvetica, 14, PdfFontStyle.Bold)
                Dim t3 = New itextsharp.text.Font(Helvetica, 12, PdfFontStyle.Bold)
                Dim t4 = New itextsharp.text.Font(Helvetica, 12, PdfFontStyle.Italic)
                Dim t5 = New itextsharp.text.Font(Helvetica, 10, PdfFontStyle.Italic)
 
                Dim logo = itextsharp.text.Image.GetInstance(Server.MapPath("~/images/farmakim logo.png"))
                logo.SpacingAfter = 10
                logo.ScaleAbsolute(50, 210)
                Dim Empty As New PdfPTable(3)
                Empty.SetWidths(New Integer() {100, 440, 100})
                Empty.DefaultCell.BorderColor = BaseColor.WHITE
                Empty.TotalWidth = 150
                Empty.SpacingBefore = 100
                Empty.DefaultCell.VerticalAlignment = PdfAlignmentStyle.MiddleCenter
                Empty.DefaultCell.FixedHeight = 100
                Empty.AddCell("")
                Empty.AddCell(logo)
                Empty.AddCell("")
                doc.Add(Empty)
 
                Dim rn As New PdfPTable(1)
                rn.DefaultCell.FixedHeight = 20
                rn.DefaultCell.HorizontalAlignment = HorizontalAlign.Left
                rn.AddCell(New Phrase(Label1.Text + " : " + TextBox1.Text, t3))
                doc.Add(rn)
 
                Dim header As New PdfPTable(1)
                header.DefaultCell.FixedHeight = 40
                header.DefaultCell.VerticalAlignment = PdfAlignmentStyle.MiddleCenter
                header.DefaultCell.HorizontalAlignment = HorizontalAlign.Left
                header.AddCell(New Phrase(Label2.Text, t1))
                doc.Add(header)
 
                Dim atable1 As New PdfPTable(1)
                atable1.DefaultCell.BorderColorLeft = BaseColor.BLACK
                atable1.DefaultCell.BorderColorRight = BaseColor.BLACK
                atable1.DefaultCell.BorderColorBottom = BaseColor.WHITE
                atable1.DefaultCell.BorderColorTop = BaseColor.WHITE
                atable1.DefaultCell.FixedHeight = 20
                atable1.AddCell(New Phrase("" & Label3.Text & "                                    " & Label4.Text & "", t5))
                atable1.AddCell(New Phrase("" & Label5.Text & "              " & Label6.Text & "              " & Label7.Text & "", t5))
                doc.Add(atable1)
 
                Dim rTable = New PdfPTable(2)
                rTable.SetWidths(New Integer() {200, 440})
                rTable.HorizontalAlignment = PdfTextAlignment.Center
                rTable.DefaultCell.FixedHeight = 35
                rTable.DefaultCell.VerticalAlignment = PdfAlignmentStyle.MiddleCenter
                rTable.AddCell(New Phrase(Label8.Text, t3))
                rTable.AddCell(New Phrase(TextBox2.Text, t4))
                rTable.AddCell(New Phrase(Label9.Text, t3))
                rTable.AddCell(New Phrase(TextBox3.Text, t4))
                rTable.AddCell(New Phrase(Label10.Text, t3))
                rTable.AddCell(New Phrase(TextBox4.Text, t4))
                rTable.AddCell(New Phrase(Label11.Text, t3))
                rTable.AddCell(New Phrase(TextBox5.Text, t4))
                rTable.AddCell(New Phrase(Label12.Text, t3))
                rTable.AddCell(New Phrase(TextBox6.Text, t4))
                rTable.AddCell(New Phrase(Label13.Text, t3))
                rTable.AddCell(New Phrase(TextBox7.Text, t4))
                rTable.AddCell(New Phrase(Label14.Text, t3))
                rTable.AddCell(New Phrase(RadioButtonList1.SelectedItem.Text, t4))
                rTable.AddCell(New Phrase(Label15.Text, t3))
                rTable.AddCell(New Phrase(RadioButtonList2.SelectedItem.Text, t4))
                doc.Add(rTable)
 
                Dim dtable = New PdfPTable(2)
                dtable.SetWidths(New Integer() {200, 440})
                dtable.DefaultCell.FixedHeight = 50
                dtable.AddCell(New Phrase(Label16.Text, t3))
                dtable.AddCell(New Phrase(TextBox8.Text, t4))
                doc.Add(dtable)
 
                Dim wtable = New PdfPTable(2)
                wtable.SetWidths(New Integer() {200, 440})
                wtable.DefaultCell.FixedHeight = 120
                wtable.AddCell(New Phrase(Label17.Text, t3))
                wtable.AddCell(New Phrase(TextBox9.Text, t4))
                doc.Add(wtable)
 
                Dim stable = New PdfPTable(2)
                stable.SetWidths(New Integer() {320, 320})
                stable.DefaultCell.FixedHeight = 60
                stable.AddCell(New Phrase("Servis Mühendisi", t3))
                stable.AddCell(New Phrase("Kurum Yetkilisi", t3))
                stable.AddCell(New Phrase("İmza", t3))
                stable.AddCell(New Phrase("İmza", t3))
                doc.Add(stable)
 
                doc.Close()
                writer.Close()
 
                Response.ContentType = "application/pdf"
                Response.AddHeader("content-disposition", String.Format("attachment;filename=Rapor-No-{0}.pdf", TextBox1.Text))
                Response.OutputStream.Write(output.GetBuffer(), 0, output.GetBuffer().Length)
            End Using
        End If
    End Sub

And here is my aspx form.

<%@ Page Language="vb" AutoEventWireup="false" CodeBehind="TSR_Newreport.aspx.vb" Inherits="TSR_Web_vb.TSR_Newreport" %>
 
 
<!DOCTYPE html>
 
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<link href="deneme.css" rel="stylesheet" />
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
    <title></title>
<style type="text/css">
    .vertical {
        height:40px;
        display:flex;
        align-items:center;
    }
    .descs{
        height:80px;
        display:flex;
        align-items:center;
    }
    .works{
        height:140px;
        display:flex;
        align-items:center;
    }
</style>
 
</head>
<body style="background-color:lightslategray">
    <center>
        <form id="form1" runat="server">
            <asp:Panel ID="Panel1" runat="server" style="height:842px; width:595px">
            <div style="height:842px; width:595px">
                <div>
                    <asp:Image ID="Image1" runat="server" ImageUrl="~/images/farmakim logo.png" Height="50px"></asp:Image>
                </div>
                <br />
                <div  style="border:solid thin black">
                    <table>
                        <tr>
                            <td>
                                <asp:Label ID="Label1" runat="server" Text="Rapor Numarası" Width="150px" Font-Bold="True" Font-Names="Helvetica" Font-Size="14px"></asp:Label>
                            </td>
                            <td>
                                <asp:TextBox ID="TextBox1" runat="server" Width="120px" Font-Names="Arial" Font-Size="12px"></asp:TextBox>
                            </td>
                        </tr>
                    </table>
                </div>
                <div style="border-left:thin solid black; border-bottom:thin solid black; border-right:thin solid black">
                    <asp:Label ID="Label2" runat="server" Text="TEKNİK SERVİS RAPORU" Font-Names="helvetica" Font-Size="24px" Font-Bold="true"></asp:Label>
                    <br />
                    <table>
                        <tr>
                            <td style="text-align:left">
                                <asp:Label ID="Label3" runat="server" Text="Tekstilkent A 24 Blok No:11 Esenler/İstanbul/Türkiye" Font-Names="Helvetica" Font-Size="12px" Width="391px" Font-Italic="True"></asp:Label>
                            </td>
                            <td style="text-align:right">
                                <asp:Label ID="Label4" runat="server" Text="Web : www.farmakim.com" Font-Names="Helvetica" Font-Size="12px" Width="189px" Font-Italic="True"></asp:Label>
                            </td>
                        </tr>
                    </table>
                    <table>
                        <tr>
                            <td style="text-align:left">
                                <asp:Label ID="Label5" runat="server" Text="Telefon: [phone]" Font-Names="Helvetica" Font-Size="12px" Width="192px" Font-Italic="True"></asp:Label>
                            </td>
                            <td style="text-align:center">
                                <asp:Label ID="Label6" runat="server" Text="Faks: [phone]" Font-Names="Helvetica" Font-Size="12px" Width="192px" Font-Italic="True"></asp:Label>
                            </td>
                            <td style="text-align:right">
                                <asp:Label ID="Label7" runat="server" Text="Mail: [e-mail]" Font-Names="Helvetica" Font-Size="12px" Width="192px" Font-Italic="True"></asp:Label>
                            </td>
                        </tr>
                    </table>
                </div>
                <div style="height:41px; text-align:left; border-left:thin solid black; border-bottom:thin solid black; border-right:thin solid black">
                    <div class="vertical" style="float:left; width:39%">
                        &nbsp&nbsp&nbsp<asp:Label ID="Label8" runat="server" Text="Rapor Tarihi" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px"></asp:Label>                        
                    </div>
                    <div class="vertical" style="width:59%; float:right; height:40px; ">
                        <asp:TextBox ID="TextBox2" runat="server" Width="340px" TextMode="Date" Font-Names="Arial" Font-Size="12px"></asp:TextBox>
                        
                    </div>
                </div>
                <div style="height:41px;  text-align:left; border-left:thin solid black; border-bottom:thin solid black; border-right:thin solid black ">
                    <div class="vertical" style="width:39%; float:left; height:40px;">
                        &nbsp&nbsp&nbsp<asp:Label ID="Label9" runat="server" Text="Kurum Adı" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px"></asp:Label>
                    </div>
                    <div class="vertical" style="width:59%; float:right; height:40px; ">
                        <asp:TextBox ID="TextBox3" runat="server" Width="340px" Font-Names="Arial" Font-Size="12px"></asp:TextBox>
                    </div>
                </div>
                <div style="height:41px;  text-align:left; border-left:thin solid black; border-bottom:thin solid black; border-right:thin solid black">
                    <div class="vertical" style="width:39%; float:left; height:40px; ">
                        &nbsp&nbsp&nbsp<asp:Label ID="Label10" runat="server" Text="Cihazın Markası" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px"></asp:Label>
                    </div>
                    <div class="vertical" style="width:59%; float:right;height:40px; ">
                        <asp:TextBox ID="TextBox4" runat="server" Width="340px" Font-Names="Arial" Font-Size="12px"></asp:TextBox>
                    </div>
                </div>
                <div style="height:41px;  text-align:left; border-left:thin solid black; border-bottom:thin solid black; border-right:thin solid black">
                    <div class="vertical" style="width:39%; float:left; height:40px;">
                        &nbsp&nbsp&nbsp<asp:Label ID="Label11" runat="server" Text="Cihazın Modeli" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px"></asp:Label>
                    </div>
                    <div class="vertical" style="width:59%; float:right; height:40px;">
                        <asp:TextBox ID="TextBox5" runat="server" Width="340px" Font-Names="Arial" Font-Size="12px"></asp:TextBox>
                    </div>
                </div>
                <div style="height:41px;  text-align:left; border-left:thin solid black; border-bottom:thin solid black; border-right:thin solid black">
                    <div class="vertical" style="width:39%; float:left; height:40px;">
                        &nbsp&nbsp&nbsp<asp:Label ID="Label12" runat="server" Text="Seri Numarası" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px"></asp:Label>
                    </div>
                    <div class="vertical" style="width:59%; float:right; height:40px;">
                        <asp:TextBox ID="TextBox6" runat="server" Width="340px" Font-Names="Arial" Font-Size="12px"></asp:TextBox>
                    </div>
                </div>
                <div style="height:41px;  text-align:left; border-left:thin solid black; border-bottom:thin solid black; border-right:thin solid black">
                    <div class="vertical" style="width:39%; float:left; height:40px;">
                        &nbsp&nbsp&nbsp<asp:Label ID="Label13" runat="server" Text="Servis Mühendisi" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px"></asp:Label>
                    </div>
                    <div class="vertical" style="width:59%; float:right; height:40px;">
                        <asp:TextBox ID="TextBox7" runat="server" Width="340px" Font-Names="Arial" Font-Size="12px"></asp:TextBox>
                    </div>
                </div>
                <div style="height:61px;  text-align:left; border-left:thin solid black; border-bottom:thin solid black; border-right:thin solid black">
                    <div class="vertical" style="width:39%; float:left; height:60px;">
                        &nbsp&nbsp&nbsp<asp:Label ID="Label14" runat="server" Text="Servis Nedeni" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px"></asp:Label>
                    </div>
                    <div class="vertical" style="width:59%; float:right;height:60px;">
                        <asp:RadioButtonList ID="RadioButtonList1" runat="server" RepeatColumns="4" RepeatDirection="Horizontal" Width="340px" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px" AutoPostBack="True">
                            <asp:ListItem>Montaj</asp:ListItem>
                            <asp:ListItem>Bakım</asp:ListItem>
                            <asp:ListItem>Arıza</asp:ListItem>
                            <asp:ListItem>Kontrol</asp:ListItem>
                            <asp:ListItem>Eğitim</asp:ListItem>
                            <asp:ListItem>Uygulama</asp:ListItem>
                            <asp:ListItem>Değişiklik</asp:ListItem>
                        </asp:RadioButtonList>
                    </div>
                </div>
                <div style="height:41px;  text-align:left; border-left:thin solid black; border-bottom:thin solid black; border-right:thin solid black">
                    <div class="vertical" style="width:39%; float:left; height:40px;">
                        &nbsp&nbsp&nbsp<asp:Label ID="Label15" runat="server" Text="Cihazın Durumu" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px"></asp:Label>
                    </div>
                    <div class="vertical" style="width:59%; float:right; height:40px;">
                        <asp:RadioButtonList ID="RadioButtonList2" runat="server" RepeatDirection="Horizontal" Width="340px" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px" AutoPostBack="True">
                            <asp:ListItem>Ücretli</asp:ListItem>
                            <asp:ListItem>Garantili</asp:ListItem>
                            <asp:ListItem>Kontratlı</asp:ListItem>
                        </asp:RadioButtonList>
                    </div>
                </div>
                <div style="height:80px;  text-align:left; border-left:thin solid black; border-bottom:thin solid black; border-right:thin solid black">
                    <div class="descs" style="width:39%; float:left">
                        &nbsp&nbsp&nbsp<asp:Label ID="Label16" runat="server" Text="Açıklama" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px"></asp:Label>
                    </div>
                    <div class="descs" style="width:59%; float:right">
                        <asp:TextBox ID="TextBox8" runat="server" Height="70px" Width="340px" TextMode="MultiLine" style="resize:none" Font-Names="Arial" Font-Size="12px"></asp:TextBox>
                    </div>
 
                </div>
                <div style="height:140px;  text-align:left; border-left:thin solid black; border-bottom:thin solid black; border-right:thin solid black">
                    <div class="works" style="width:39%; float:left">
                        &nbsp&nbsp&nbsp<asp:Label ID="Label17" runat="server" Text="Yapılan İşler" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px"></asp:Label>
                    </div>
                    <div class="works" style="width:59%; float:right">
                        <asp:TextBox ID="TextBox9" runat="server" Height="130px" Width="340px" TextMode="MultiLine" style="resize:none" Font-Names="Arial" Font-Size="12px"></asp:TextBox>
                    </div>
                </div>
                <div style="height:100px; border-left:thin solid black; border-bottom:thin solid black; border-right:thin solid black">
                    <div style="height:100px; width:49%; float:left; text-align:left; border-right:thin solid black">
                        &nbsp;&nbsp;&nbsp;
                        <asp:Label ID="Label18" runat="server" Text="Servis Mühendisi" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px"></asp:Label>
                        <br />
                        <br />
                        &nbsp;&nbsp;&nbsp;
                        <asp:Label ID="Label19" runat="server" Text="İmza" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px"></asp:Label>
                    </div>
                    <div style="height:100px; width:49%; float:right; text-align:left">
                        <asp:Label ID="Label20" runat="server" Text="Kurum Yetkilisi" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px"></asp:Label>
                        <br />
                        <br />
                        <asp:Label ID="Label21" runat="server" Text="İmza" Font-Bold="True" Font-Names="Helvetica" Font-Size="12px"></asp:Label>
                    </div>
                </div>
            </div>
            </asp:Panel>
            <br />
            <br />
            <asp:Button ID="Button1" runat="server" Text="Print" OnClick="Button1_Click" Width="100px"></asp:Button>
            &nbsp&nbsp&nbsp<asp:Button ID="Button2" runat="server" Text="Formu Temizle" Width="100px"></asp:Button>
            &nbsp&nbsp&nbsp<asp:Button ID="Button3" runat="server" Text="İptal" Width="100px"></asp:Button>
        </form>
    </center>
</body>
</html>

I believe there is someone that who can help me.

Thank you

Answer 1

User-1330468790 posted

Hi N.Elverdi,

  

I did the test with your codes and found out that the error could not be thrown in the given point

Dim writer = PdfWriter.GetInstance(doc, output)

It seems impossible to get the Null-Reference exception since you don't even try to access the variables doc and output.

However, if I don't select an item in lists "RadioButtonList1" and "RadioButtonList2", I will get a null reference exception from below codes:

rTable.AddCell(New Phrase(RadioButtonList1.SelectedItem.Text, t4))
rTable.AddCell(New Phrase(Label15.Text, t3))
rTable.AddCell(New Phrase(RadioButtonList2.SelectedItem.Text, t4))             

The reason is that the SelectedItem is null and you are trying to access the property "Text" of null.

Test condition which successfully produces a PDF:

•  TextBox 1~6 are assigned with value
• Both RadioButtonList1 and RadioButtonList2 are assigned with a default selected value

 

Could you please check if it is the reason?

 

Reminder for protecting company/personal information:

I noticed that you have included some company/personal information (Phone, Address, etc) in the codes. Please delete them (modify them with foo/bar-like information) to protect your secure information. We will not save any company/personal information but the forum is an open and public environment.

  

Hope helps.

Best regards,

Sean

Answer 2

User-1062969975 posted

Dear Sean,

Thank you for you quick reply. I have tried again with filling radiobuttonlists by me and it appears same error. I have add some screen shots.

https://www.dosya.tc/server31/wzl0k0/01.JPG.html

https://www.dosya.tc/server31/6dgvs9/02.JPG.html

I hope it will help you to see more information.

Answer 3

User-1062969975 posted

Sean, I think I found problem,

<a href="https://www.imageupload.net/image/tzUpk"><img src="https://img.imageupload.net/2020/10/15/02.jpg" alt="02.jpg" border="0" /></a>

When I checked itextsharp.dll it worked

Answer 4

User-1330468790 posted

Hi N.Elverdi,

  

Glad to see that you have solved the problem.

I didn't expect that VS would miss a reference and trigger that error.

From my side, I directly let VS download any iTextShart package using the quick action and refactoring helper. 

  

Best regards,

Sean