GenerateAppearances = true; System.NullReferenceException

Question

Got some legacy code using iTextSharp.

All documents have GenerateAppearances set to true regardless. and now its triggering an exception.

Took the basic code out and placed it into a Console app, same thing, Used a generic PDF (http://www.pdf995.com/samples/pdf.pdf) of the net same thing.

This is using version 5.5.12

class Program
{
    static void Main(string[] args)
    {
        var reader = new PdfReader(@"C:\Users\me\Desktop\pdf.pdf"); 

        var outStream = new MemoryStream();
        var stamper = new PdfStamper(reader, outStream);

        stamper.AcroFields.GenerateAppearances = true; <--- usually true before setting
        stamper.FormFlattening = true;
    }
}

An unhandled exception of type 'System.NullReferenceException' occurred in itextsharp.dll

Additional information: Object reference not set to an instance of an object.

Thanks

Define legacy code. Are you talking about an iTextSharp version that is several years old? In that case, the question risks to be closed for the following reason: "This question was caused by a problem that can no longer be reproduced." — Bruno Lowagie, Nov 08 '17 at 12:23
OK, in that case it surprises me that you have to set `GenerateAppearances` to `true`. Have you checked if `stamper.AcroFields` is not `null`? It is normal that you get a `NullReferenceException` in case you process a document that isn't an AcroForm (it may look like a form to the human eye, but that doesn't mean it's a form to a machine). — Bruno Lowagie, Nov 08 '17 at 12:48
AcroFields is not null. GenerateAppearances is true all before assigning true again. Triggers an exception: System.NullReferenceException.Data: ListDictionaryInternal Count is 0 — Michael Kearney, Nov 08 '17 at 12:52

score 1 · Answer 1 · edited Jan 18 '22 at 15:46

1

After years of production, I just changed it from:

if (stamper.AcroFields != null)
{
    f.GenerateAppearances = true;

    foreach(var field in f.Fields)
    {
        f.SetField(field.Key, f.GetField(field.Key));
    }

    stamper.FormFlattening = true;
}

to

if (stamper.AcroFields != null && stamper.AcroFields.GenerateAppearances == true)

edited Jan 18 '22 at 15:46

Saeid Amini

1,313
5
16
26

answered Nov 08 '17 at 14:55

Michael Kearney

31
5

I'm not sure if I understand the change, but I'm glad to see that you were able to fix the problem. – Bruno Lowagie Nov 08 '17 at 15:00

score 0 · Answer 2 · answered Jan 10 '22 at 06:37

0

I encounter the same issues as below: When I set AcroFields.GenerateAppearances = true an unhandled exception of type 'System.NullReferenceException' occurred in itextsharp.dll Additional information: Object reference not set to an instance of an object.

I debugged this code and found that AcroFields is not null. but NullReferenceException still occourred.

After inverstigating, I found that the format of PDF file is aspose xfa rather than acroforms. So I solved this issue by converting the format of PDF from aspose xfa to acroforms.

answered Jan 10 '22 at 06:37

Jean Huang

1

What do you mean by "*aspose* xfa"? XFA is a semi-proprietary *Adobe* format... – mkl Jan 10 '22 at 09:06
As it’s currently written, your answer is unclear. Please [edit] to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Community Jan 10 '22 at 09:33

GenerateAppearances = true; System.NullReferenceException

2 Answers2