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PDF comparison API license issue in .NET


We are using GroupDocs.Total (Enterprise) for .NET for file comparison. While trying to compare pdf files an error throws and no result is produced and on checking we found the LIC file having a date which seems to be expired one. Is the issue caused due to this? Other type of file comparisons are working fine though(eg: word,excel).

Error details:

sourceStream.ReadTimeout’ threw an exception of type ‘System.InvalidOperationException’/ ,result.ReadTimeout’ threw an exception of type 'System.InvalidOperationException

Please find the LIC file subscription details below:


1 Like


Thanks for posting your concerns.

In order to investigate this issue at our end, we need following details from you:

  • API version (e.g. 18.7, 18.7.1)
  • Problematic PDF files (source and target)
  • Sample code for PDF comparison

Please share the output file.

Dear Atir,

We are using GroupDocs.Comparison dll for that. Its version is 3.3.0. Also GroupDocs Viewer dll version is 17.5.0. Our client has escalated this issue and please provide a resolution for this asap.

Please find the below code:

string sourceFileName = null;
string targetFileName = null;
string diffFileName = null;
GroupDocs.Comparison.Comparison comparison = new GroupDocs.Comparison.Comparison();
sourceFileName = Source + “_src” + data.DownloadAttachmentDTOs.FileExtn;
targetFileName = Target + “_trg” + data.DownloadAttachmentDTOs.FileExtn;
diffFileName = Target + “_diff” + data.DownloadAttachmentDTOs.FileExtn;

result = comparison.Compare(Path.Combine(Server.MapPath(curUserFolder), sourceFileName), Path.Combine(Server.MapPath(curUserFolder), targetFileName), Path.Combine(Server.MapPath(curUserFolder), diffFileName), ComparisonType.Pdf);

The pdf files cant be attached due to privacy issues.


We reproduced this issue at our end using an expired license. In the case of expired license, there still must be a successful PDF comparison (as for Word or Excel formats). And of course output will endure evaluation limitations.
Hence, we have logged this issue in our internal issue tracking system with ID:COMPARISONNET-1663. We shall update you as we have any further updates on it.

Yes, you’ve to renew your license in order to get rid of this exception.

However, API compares both Word or Excel files (using expired license) with an evaluation mark in the output file.

Dear Atir,

But we have purchased a lifetime licenced version of GroupDocs.Total (Enterprise). So please advice how to renew this further.


Your license file subscription seems to be expired.

You can renew your order here. And if you have any purchase related queries, you can post in purchase category.


We further investigated this behavior and noted that API returns only 4 elements from every collection without a license or expired license. So we can’t get necessary object model to build document. That is why exception happens. The only solution is to avail or renew a license.

We already have a perpetual license, we would like to continue with that please advise.

Also attaching the details of license type we purchased.


Please share your license file with us in a private message.


Good Morning.

Could you please provide any email address for sharing the same?.



Good Morning.
Please click on my profile, there you will see a Message button. Just like this - PrivateMessage.jpeg (13.0 KB). Using that you can share the license file.

I have sent the License files are private message.
Please note that the License file also tells that the Subscription End date is Aug,
But my BIG question still remains that our is a Perpetual license “GroupDocs.Total for.NET”,
How that could expire?

Also please note that our clients are getting affected because of this. Is there a Priority Support or Hot line for us to expedite the process!!


The subscription must not affect your license. You can utilize it with any version of the API that is released before your subscription expiry date. Therefore, you cannot integrate a new version of the API released after your subscription expiry date.

We are investigating your issue. However, if you want to expedite the process, you can avail our priority support.

Please consider this as a high priority as we have serious impacts in our clients.
Kindly provide us a temporary license till you fix the issue permanently .


You can avail temporary license on step 5 here. Please follow the steps given in the attached document/wizard in order to get a temporary license successfully - (152.9 KB)

This issue is under investigation. We shall update you as we have any update.

Any updates?


This issue is still under investigation. We shall notify you as we have any update. Your patience shall be appreciated in this regard.


We investigated the sample project using problematic files you shared with us (in private message). This is a back-end API related issue not license.
Hence, it will be fixed in upcoming release (18.9). As release gets on-board, we shall notify you.

Thanks , could you please advice what is wrong with the document, so that we can advise our users temporarily to correct the same and proceed.


At the moment, we could not say that what is exactly wrong with these documents.