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How to manage memory while merging large WinForms PDF documents?

2 mins read

Setting the EnableMemoryOptimization property of the PdfLoadedDocument to true reduces the memory usage when its instance is closed in WinForms PDF.  To achieve this, create a PdfDocument, then import the pages and contents of the loaded documents to the PdfDocument, and dispose the loaded document. Finally, save the PdfDocument’s instance and close the same.

C#

//Gets the file directory
String[] inputDocuments = Directory.GetFiles("../../Data/");
//Creates a new instance.
PdfDocument document = new PdfDocument();
//Optimizes memory while merging PDF documents.
document.EnableMemoryOptimization = true; 
//Iterates input PDF documents.
 foreach (string inputDocument in inputDocuments)
{
//Loads PDF document in order to merge.
PdfLoadedDocument loadedDocument = new PdfLoadedDocument(inputDocument);
loadedDocument.EnableMemoryOptimization = true;
//Merges loaded document contents to the parent PDF document. 
document.ImportPageRange(loadedDocument, 0, loadedDocument.Pages.Count - 1); 
//Closes the document.
loadedDocument.Close(true); 
}
//Saves and closes the document.
document.Save("Output.pdf");
document.Close(true);

Sample Link:


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Conclusion:

I hope you enjoyed learning about how to manage memory while merging large WinForms PDF documents.

 

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Comments (1)
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AW
Andrew Williams
I'm getting an "Object reference not set to an instance of an object" exception when I use this method with streams instead of file paths. Everything works until I go to save the document. The code doesn't crash if I take out "loadedDocument.Close(true);".

at Syncfusion.Pdf.Primitives.PdfReferenceHolder.get_Index()
   at Syncfusion.Pdf.Primitives.PdfReferenceHolder.GetObject()
   at Syncfusion.Pdf.Primitives.PdfReferenceHolder.get_Object()
   at Syncfusion.Pdf.Primitives.PdfReferenceHolder.Save(IPdfWriter writer)
   at Syncfusion.Pdf.Primitives.PdfDictionary.SaveItems(IPdfWriter writer)
   at Syncfusion.Pdf.Primitives.PdfDictionary.Save(IPdfWriter writer, Boolean bRaiseEvent)
   at Syncfusion.Pdf.Primitives.PdfDictionary.Save(IPdfWriter writer)
   at Syncfusion.Pdf.Primitives.PdfDictionary.SaveItems(IPdfWriter writer)
   at Syncfusion.Pdf.Primitives.PdfDictionary.Save(IPdfWriter writer, Boolean bRaiseEvent)
   at Syncfusion.Pdf.Primitives.PdfDictionary.Save(IPdfWriter writer)
   at Syncfusion.Pdf.Primitives.PdfDictionary.SaveItems(IPdfWriter writer)
   at Syncfusion.Pdf.Primitives.PdfDictionary.Save(IPdfWriter writer, Boolean bRaiseEvent)
   at Syncfusion.Pdf.Primitives.PdfStream.Save(IPdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.DoSaveObject(IPdfPrimitive obj, PdfReference reference, PdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.SaveIndirectObject(IPdfPrimitive obj, PdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.SaveObjects(PdfWriter writer)
   at Syncfusion.Pdf.IO.PdfCrossTable.Save(PdfWriter writer)
   at Syncfusion.Pdf.Parsing.PdfLoadedDocument.AppendDocument(PdfWriter writer)
   at Syncfusion.Pdf.Parsing.PdfLoadedDocument.Save(Stream stream)
AW
Andrew Williams
Figured out what I was doing wrong, make sure you Enable Memory Optimization on the Document as well as the loadedDocuments. I forgot to do the former, which I guess leaves behind some references to the pdfs that are loaded into it.
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