Troubleshooting 404 Not Found in ASP.NET Core

Описание: Discover how to resolve the `404 Not Found` error in ASP.NET Core when retrieving data by ID and learn best practices for structuring your API
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This video is based on the question https://stackoverflow.com/q/63747371/ asked by the user 'Cristian Flaviu' ( https://stackoverflow.com/u/11761764/ ) and on the answer https://stackoverflow.com/a/63747688/ provided by the user 'Wellington Júnior' ( https://stackoverflow.com/u/13972593/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting 404 Not Found in ASP.NET Core: A Beginner's Guide

If you're new to C# and ASP.NET Core, encountering HTTP errors can be quite frustrating. One common issue is receiving a 404 Not Found response when trying to retrieve or delete a resource, such as a company by its ID. This guide will guide you through understanding the problem and how to implement effective solutions to avoid this issue in the future.

Understanding the 404 Not Found Error

The 404 Not Found error indicates that the requested resource could not be found on the server. In your case, you are trying to access the following endpoint to get a company by its ID:

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This request is failing and returning a 404 status, while your endpoint for retrieving all companies works perfectly fine:

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What Could Cause the 404 Not Found Error?

There are a couple of common reasons for receiving a 404 Not Found error in ASP.NET Core:

Incorrect Routing: The route specified in your controller might not be set up correctly.

Improper Parameter Binding: The way the method parameters are defined may not align with the expected route format.

Solution: Fixing the Routing Issue

Your current CompanyController has an issue with how the routing for the GetCompanyById method is defined. Here's the original method you provided:

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While you correctly used HttpGet, the route configuration is leading to confusion. The code is expecting a query parameter, but the intended use is to pass the ID directly in the URL.

Recommended Changes to the Code

To resolve the 404 Not Found error, follow these steps to update the GetCompanyById method:

Combine Route Attributes: Use a single HttpGet attribute with the expected route format.

Change the Parameter Binding: Instead of using [FromQuery], use the method parameter directly.

Here’s how your updated code should look:

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Best Practices

Although the above change will resolve the immediate issue, it's also good to consider how you structure your API for future reference. A cleaner approach for the GetCompanyById call could be to simplify the route, omitting the need for the action name altogether. You can define the route as follows:

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By doing this, the endpoint would now simply be:

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This not only makes the URL cleaner but also aligns with RESTful API design principles.

Conclusion

Receiving a 404 Not Found error can be an indication of routing issues in your ASP.NET Core application. By ensuring your routes are correctly defined and structured according to best practices, you can significantly reduce these errors and create a more efficient and user-friendly API. Remember to keep experimenting and learning; building robust applications takes time and practice.

If you continue to experience issues, don’t hesitate to reach out to online communities for additional support. Happy coding!