Best Approach to Automatically Import and Unzip Large ZIP Files in SharePoint Online from a Custom Angular/.NET Core Application

Question

Hello,

I’m developing a web application using Angular (front-end) and ASP.NET Core (back-end). The application interacts with SharePoint Online using SharePoint CSOM (C#). One of our key use cases is to allow clients to upload complex and potentially large ZIP files directly into SharePoint Online via our application.

Once the ZIP file is received, we need to automatically extract its contents (which may include deep folder structures and thousands of files) and store the extracted files back into SharePoint Online in the appropriate location.

I would like guidance on the most efficient and scalable way to handle this process. Specifically:

• Should we use CSOM to handle the ZIP decompression and file upload?

Would Power Automate be a better fit for triggering and processing the ZIP content?

Could the SharePoint Migration Tool or API help in this case?

Are there other recommended Microsoft services or APIs for this kind of automated ZIP file extraction and import into SharePoint Online?

Our main constraints are:

The process must be fully automated for the user (no manual steps after upload).

It must be able to handle large files and nested folder structures.

It should integrate smoothly into our existing backend and SharePoint Online.

Thank you in advance for your insights and guidance on best practices for this scenario.

Answer 1

Utilizing CSOM and Power Automate for ZIP decompression and file upload are not optimal for large files with deep folder structures.

The SharePoint Migration Tool (SPMT) is primarily designed for migrating content from on-premises SharePoint sites and file shares to SharePoint Online. While it excels in bulk data migration scenarios, it doesn't specifically cater to the real-time extraction and organization of ZIP file contents. Therefore, it may not be the most suitable choice for your use case.​

For a scalable and efficient solution, consider implementing Azure Functions in conjunction with Azure Blob Storage.

Azure Blob Storage: Store the uploaded ZIP files in Azure Blob Storage. This service is optimized for handling large files and offers high availability and scalability.​

Azure Functions: Develop serverless functions that trigger upon the arrival of a new ZIP file in Blob Storage. These functions can efficiently extract the ZIP contents, maintain the folder structure, and upload the files to SharePoint Online using CSOM or the REST API.

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