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We are able to reproduce the reported issue “XlsIO Saved file does not open in MS Excel” from our side. We suspect that this could be an issue and send to the development team for further analysis. We request you to create a new incident to further follow up on this issue.
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The memory issue reported earlier was an usage issue. This issue can be resolved by resetting the memory stream position to zero before copying the memory stream to file stream. Please follow the below code snippet to resolve the issue.
MemoryStream ms = new MemoryStream();
//Resetting Memory stream position.
ms.Position = 0;
FileStream file = new FileStream(Server.MapPath("App_data/Output.xlsx"), FileMode.Create, System.IO.FileAccess.Write);
byte bytes = new byte[ms.Length];
ms.Read(bytes, 0, (int)ms.Length);
file.Write(bytes, 0, bytes.Length);
If you are unable to resolve the issue, please share us your entire scenario and the code snippet which will be helpful for us to give you a prompt solution.
Please let us know if you have any concerns.