Скачать или смотреть How to Handle HTTP Error 413.1 - Request Entity Too Large Without Crashing Your Site

Learn how to gracefully handle HTTP Error 413.1 by preventing file uploads that are too large, without disrupting your site's functionality.
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This video is based on the question https://stackoverflow.com/q/65601449/ asked by the user 'Forrest' ( https://stackoverflow.com/u/10350396/ ) and on the answer https://stackoverflow.com/a/65607788/ provided by the user 'Ding Peng' ( https://stackoverflow.com/u/11774618/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding HTTP Error 413.1 - Request Entity Too Large

Have you ever tried to upload a large file only to be met with the dreaded HTTP Error 413.1 - Request Entity Too Large? This error can be frustrating—not just because it signals a problem with the file size, but also because it can crash your entire site. When this happens, visitors are greeted with an error page instead of the content they're trying to access. But what if you want to handle large file uploads more gracefully? Let's explore how you can achieve that.

The Problem: Crashing the Site

When an ASP.NET Core application is hosted in IIS, the web server has a built-in limit on the file size it will accept. If a user attempts to upload a file that exceeds this limit, IIS throws the HTTP Error 413.1. Here are some key points about this issue:

This error disrupts the entire site, leading to a poor user experience.

Increasing the file size limit in IIS isn't always the desired solution, especially if you want to maintain control over the uploaded data.

The Solution: Pre-emptively Validate File Size

Instead of relying solely on IIS to enforce file size limitations, we can implement a strategy that allows for client-side validation. This way, you'll provide immediate feedback to users if their file is too large, ensuring that they won’t hit the IIS error.

Step-by-Step Guide

Client-Side JavaScript Validation:

Use JavaScript to check the file size before the file is submitted to the server.

This prevents unnecessary server requests and keeps users informed without exposing them to error pages.

Here’s an example JavaScript code snippet that demonstrates how to validate file size on the client side:

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

Explanation of the Code

document.getElementById('fileId').files: This accesses the file input element and checks how many files are selected.

files[0].size: This retrieves the size of the first file selected.

The conditional check (fileSize > 1048576) determines if the file exceeds the 1MB limit, displaying an alert if it does.

Backend Validation (Optional):

Even though you’ve implemented client-side checks, it is always a good practice to validate on the server side as well. This ensures the server handles any edge cases where users might bypass client-side checks.

You can maintain your ASP.NET Core view model with the existing size validation logic.

Sample View Model Validation

Your existing code for the view model can stay the same, simply to reinforce validation on the server side:

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

Conclusion

By implementing client-side validation for file uploads, you can manage the user experience better and prevent the disruption caused by the HTTP Error 413.1. Not only does it ensure users are informed before they attempt to upload large files, but it also reduces unnecessary server load—keeping your site running smoothly.

Take control of file uploads today and provide a seamless experience for your users!