Creating a new Document with a FileStream with Aspose.Pdf

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I'm trying to create a new Aspose.Pdf.Document using a FileStream to a new File, but it always throws an "Incorrect File Header" Exception. I need to work with the FileStream so that I can incrementally save the Document when merging other Pdf documents without keeping all of the Streams in scope.

According to the documentation, the following is the code to create a Document with a FileStream (I changed FileMode.Open to FileMode.OpenOrCreate since I don't have an existing Pdf file and want to start with a blank Document).

await using var fileStream = new FileStream(fileName, FileMode.OpenOrCreate, FileAccess.ReadWrite);
var document = new Document(fileStream);

This code throws an "Incorrect File Header" Exception unless the FileStream points to an existing valid Pdf file.

The following code works, but it's kind of silly to create and dispose a Document just so that we can work with the Document through the FileStream.

var fileName = Path.GetTempFileName();
var doc = new Document();
doc.Save(fileName);
doc.Dispose();

await using var fileStream = new FileStream(fileName, FileMode.Open, FileAccess.ReadWrite);
var document = new Document(fileStream);

I have to be missing something painfully obvious, because this is an incredibly simple use case and I don't see anything about it when searching online.

aspose.pdf c#
1 Answers

You cannot initialize the Document object with an empty Stream or invalid PDF file. File or Stream should be a valid PDF document. In order to use the incremental saving approach, you can initialize the FileStream with a new file and keep saving the Document into it. For example, please check the below sample code snippet:

using var fileStream = new FileStream(dataDir + "output.pdf", FileMode.OpenOrCreate, FileAccess.ReadWrite);
{
 var document = new Document();
 document.Pages.Add();
 document.Save(fileStream);
 document.Pages.Add();
 document.Save(fileStream);
}

Please note that the FileStream needs to remain open during the whole process of PDF generation. Along with that, you can also use Document.Save(); method (without any constructor) to implement incremental saving.

We believe that you have also posted a similar inquiry in Aspose.PDF official support forum and we have responded to you there as well. You can please follow up on it there and carry on the discussion in case you need more information.

This is Asad Ali and I work as Developer Evangelist at Aspose.

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