Скачать или смотреть Fixing the Corrupted Excel Files Issue When Zipping with EPPlus in C#

Learn how to resolve the issue of corrupted Excel files when generating multiple files using EPPlus and zipping them with DotNetZip in C# .
---
This video is based on the question https://stackoverflow.com/q/65068579/ asked by the user 'Atiq Baqi' ( https://stackoverflow.com/u/6160923/ ) and on the answer https://stackoverflow.com/a/65068685/ provided by the user 'user1672994' ( https://stackoverflow.com/u/1672994/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Excel file is corrupted after generating multiple excel files using EPPLUS and Zipped using DotNetZip from an ActionResult in C#

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Resolving the Corrupted Excel Files Issue When Zipping with EPPlus in C#

Introduction

Are you facing an issue where the Excel files you generate using EPPlus are corrupted after being zipped with DotNetZip in a C# ActionResult? If so, you're not alone. This is a common problem that many developers encounter when trying to export multiple Excel files as a single downloadable ZIP file. In this guide, we'll explore the cause of this problem and provide a simple solution that will allow you to successfully create a ZIP file containing multiple non-corrupted Excel files.

Understanding the Problem

When working with data that needs to be exported into multiple Excel files, using libraries like EPPlus makes the task easier. However, since a web application can only return a single file from an ActionResult, it's common to ZIP those files together. The challenge arises when these files become corrupted upon extraction from the ZIP file—typically giving an error upon opening. In this case, the issue relates to how files are saved within the ZIP archive.

Here's a quick summary of the scenario:

Goal: Export multiple Excel files and zip them for download.

Issue: After zipping, the Excel files within the ZIP archive are corrupted.

Current Implementation: Saving the ZIP file after adding each Excel file results in corruption.

The Solution

The core of the issue lies in the placement of the zip.Save(memoryStream); line in the code. By saving the ZIP file multiple times while looping through the Excel file creations, the content gets overwritten, leading to corruption.

Steps to Fix the Issue

Here’s how you can adjust your code to ensure that all files are zipped correctly without corruption:

Remove the zip.Save(memoryStream); from within the loop: This prevents the ZIP file from being saved multiple times during the addition of files.

Move the zip.Save(memoryStream); to just before returning the file: This allows all Excel files to be added to the ZIP file first before saving it.

Updated Code Example

Here’s an updated version of your ExportExcel method demonstrating the changes:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By implementing these changes, you ensure that the ZIP file only saves once, after all Excel files have been added. This should resolve the issue of corrupted files, allowing users to open each Excel file without any error. This solution not only enhances functionality but also improves user experience when exporting data.

If you continue to experience issues, check the code for any other related errors and ensure that the EPPlus and DotNetZip libraries are properly integrated into your project. Happy coding!