When adding a resource like an image to a Document from a MemoryStream the above error is thrown in the Save() method, when the stream was already closed. I could find several topics about this but none with a workable solution.
There are some worarounds I could find, but each has its own problems:
Not closing the stream until after the Document was saved: That’s not that easy when you have a more complex program (see code example at the end)
Flattening the Document before the stream is closed: This seems to force the Document to completly load the data from the stream, so you don’t get an error when saving while the stream is closed. But this only works when you actually can flatten the PDF and don’t need its form fields etc. anymore.
Validating the Document before the stream is closed: This works like flattening and seems to force the Document to load all data from the stream. But it lead to problems for us with newer PDF Versions than our Aspose Version supported.
What is the supposed way to deal with this problem when you have something like the following?
enum AttachmentType { Pdf, Image }
class Attachment
{
public AttachmentType AttachmentType { get; set; }
public byte[] Data { get; set; }
}
static void AttachmentTest()
{
Document document = new Document();
AddAttachments(document, new List<Attachment>()
{
new Attachment() { AttachmentType = AttachmentType.Pdf, Data = File.ReadAllBytes(@"c:\test\1.pdf") },
new Attachment() { AttachmentType = AttachmentType.Image, Data = File.ReadAllBytes(@"c:\test\1.jpg") }
});
byte[] result;
using (MemoryStream pdfStream = new MemoryStream())
{
document.Save(pdfStream); //throws an Exception: "Cannot access closed stream"
result = pdfStream.ToArray();
}
}
static void AddAttachments(Document document, List<Attachment> attachments)
{
foreach (var attachment in attachments)
{
switch (attachment.AttachmentType)
{
case AttachmentType.Pdf:
AddPdf(document, attachment.Data);
break;
case AttachmentType.Image:
AddImage(document, attachment.Data);
break;
}
}
}
static void AddImage(Document document, byte[] imageData)
{
Page page = document.Pages.Add();
var image = new Image();
using (MemoryStream stream = new MemoryStream(imageData))
{
image.ImageStream = stream;
page.Paragraphs.Add(image);
}
}
static void AddPdf(Document document, byte[] pdfData)
{
using (MemoryStream stream = new MemoryStream(pdfData))
{
using var attachmentDoc = new Document(stream);
document.Pages.Add(attachmentDoc.Pages);
}
}
To me it looks like when page.Paragraphs.Add(image); does not actualy loads all the data from the stream which leads to the error.
The error “Cannot access a closed stream” typically occurs when you attempt to use a stream that has already been disposed or closed. In your case, it seems that the issue arises when saving the document to a MemoryStream after adding images and PDFs from other streams.
Here are a few suggestions to resolve this issue:
Ensure Stream Lifetime: Make sure that the streams you are using for images and PDFs remain open until after the document is saved. You can achieve this by restructuring your code to avoid disposing of the streams prematurely.
Use a Temporary Storage: Instead of directly using MemoryStream for images, consider saving the image data to a temporary file and then using the file path to load the image. This way, you avoid the issue of stream disposal. Here’s an example of how you can modify the AddImage method:
static void AddImage(Document document, byte[] imageData)
{
Page page = document.Pages.Add();
string tempImagePath = Path.GetTempFileName() + ".jpg"; // Create a temporary file
File.WriteAllBytes(tempImagePath, imageData); // Write image data to the file
var image = new Image { File = tempImagePath }; // Use the file property
page.Paragraphs.Add(image);
}
Properly Manage MemoryStream: If you prefer to keep using MemoryStream, ensure that you are not disposing of it until after the document is saved. You can do this by managing the scope of your streams carefully.
Update Aspose.PDF Version: If you are using an older version of the Aspose.PDF library, consider updating to the latest version, as there may have been fixes related to stream handling in newer releases.
By following these suggestions, you should be able to avoid the “Cannot access a closed stream” error when saving your document. If the problem persists, please check that all objects you are working with are not disposed of before you finish using them.
Sorry, but this randomly generated ai text doesn’t help at all. I explicitly created a code sample to show why “just don’t close your streams” is not a reasonable solution…
Aspose.PDF API follows DOM approach and it keeps all resources in memory until the document is saved. If a resource is in memory and its stream is closed before Save() call, the API wouldn’t be able to access it while saving the document. Therefore, current solution will be to keep memory stream opened before the document is saved or use the stream inside using statements.
We have also noticed your comments, and logged an investigation ticket as PDFNET-58713 in our issue tracking system to further investigate if some other improvements can be made for better use. We will look into details of the ticket and keep you posted with the status of its correction. Please be patient and spare us some time.
PS: A clean solution for this would be, if you added a parameter to this and similar methods that controls wether the caller wants to dispose the stream or your library is doing if after it no longer needs it (e. g. after saving).