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Learn how to efficiently download files like PDFs in .NET Core Razor Pages without encountering common errors such as ObjectDisposedException.
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This video is based on the question https://stackoverflow.com/q/67035382/ asked by the user 'MaxPowers' ( https://stackoverflow.com/u/1326980/ ) and on the answer https://stackoverflow.com/a/67036849/ provided by the user 'Andy' ( https://stackoverflow.com/u/1204153/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Return Files from URL as IActionResult in .NET Core with Razor Pages

In the modern web development landscape, enabling file downloads in your applications can sometimes feel challenging. If you're working with .NET Core and Razor Pages, you might have found yourself facing the "ObjectDisposedException" error. This issue typically arises when attempting to download files from a URL. In this post, we will explore a straightforward solution to properly return files and ensure error-free downloads.

Understanding the Problem

You're likely looking to enable users to download a PDF or another file type by clicking a button on your Razor Pages application. However, you've encountered the following error:

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This error usually occurs when a file stream is disposed before its contents have been fully utilized. In other words, your application is trying to access a file stream that is no longer available. Let's dive into the solution.

A Step-by-Step Guide to Returning a File

1. Use HttpClientFactory Instead of Creating a New HttpClient

Creating a new instance of HttpClient each time you need to make a request can lead to performance issues and inefficiencies. Instead, utilize IHttpClientFactory which helps manage HttpClient lifetimes effectively.

Inject IHttpClientFactory: Modify your Razor Page model to accept IHttpClientFactory via constructor injection.

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2. Stream the File Directly from the Response

To avoid errors related to disposed streams, stream the file directly from the web request to the response. Here's how you can implement it:

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3. Register HttpClient in Startup.cs

Finally, ensure that you have registered HttpClient in your application's service container. Update your Startup.cs file as follows:

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Conclusion

By following this structured approach, you can smoothly return files from a URL as IActionResult in your Razor Pages application. Not only does this method eliminate the common errors associated with disposed streams, but it also enhances memory efficiency by streaming directly from the source to the response.

Next time you implement file downloads, remember to leverage IHttpClientFactory and ensure that your file streams remain accessible throughout their use. This way, you’ll provide an optimal experience for your users with seamless file downloading capabilities.

Feel free to reach out in the comments if you have any further questions or need assistance!