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Discover the best method to effectively `download and unzip large ZIP files` from Azure Blob Storage without encountering the "stream too long" exception.
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Efficiently Download and Unzip Large ZIP Files from Azure Blob Storage

In today's cloud-driven world, handling large files is often a necessity. However, working with large ZIP files can lead to various challenges, especially when downloading them from Azure Blob Storage. One common issue developers face is the dreaded "stream too long" exception when attempting to download and unzip sizable ZIP files using .NET. In this guide, we will explore this problem and provide a practical solution to overcome it efficiently.

The Problem: Handling Large ZIP Files

Imagine you're working with a ZIP file that is a whopping 9GB in size. While attempting to download this file with the following method:

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

You may encounter an error that prevents you from proceeding. The error message often looks like this:

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

This error indicates that the stream of data being processed exceeds what the underlying memory structure can handle, especially when you attempt to load the entire ZIP file into memory. As we all know, this can be a significant roadblock in your work, especially if you want to keep your application efficient and responsive.

The Solution: Using OpenReadAsync

To tackle this issue, the key is to use a different method for downloading the ZIP file. Instead of utilizing DownloadAsync, we can leverage the OpenReadAsync method. This approach allows for streaming the content directly, avoiding the need to load the entire file into memory. Here's how you can do it:

Step-by-Step Implementation

Open the Blob as a Readable Stream
Replace the previous method with OpenReadAsync to allow for streaming:

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

Work with the ZIP Archive
Utilize the stream to create a ZipArchive instance:

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

Upload Each Entry to the New Container
For every entry in the archive, you can upload it directly to your desired container without writing anything to disk:

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

Full Code Example

Here is the complete code snippet implementing the changes discussed:

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

Conclusion

In this article, we faced the challenge of downloading and unzipping a large 9GB ZIP file from Azure Blob Storage that resulted in a "stream too long" exception. By switching from DownloadAsync to OpenReadAsync, we could efficiently stream the data and handle the ZIP file without overwhelming the memory.

If you're dealing with large files in your projects, adopting this method can save you from headaches and ensure smooth operations within your applications. Happy coding!