Скачать или смотреть Fixing the 404 Error on ASP.NET CORE 5 API Controller

Discover how to resolve the issue of a non-functional API controller in ASP.NET CORE 5, leading to a `404 Not Found` error.
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This video is based on the question https://stackoverflow.com/q/69959267/ asked by the user 'realPro' ( https://stackoverflow.com/u/1155216/ ) and on the answer https://stackoverflow.com/a/69959275/ provided by the user 'realPro' ( https://stackoverflow.com/u/1155216/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Fixing the 404 Error on ASP.NET CORE 5 API Controller

Working with ASP.NET CORE 5 can be a rewarding experience, but developers sometimes encounter issues that stall their progress. One such problem is when you’ve added an API controller to your project, but it simply doesn’t work, resulting in frustrating 404 Not Found errors. If you've faced this challenge, you’re not alone. In this post, we’ll explore the reasons behind this issue and provide a simple, clear solution.

Understanding the Problem

When you create an API controller in ASP.NET CORE 5 but receive a 404 error, it generally indicates that your application is unable to recognize the routes specified in your controller. Here’s a snippet of the API controller that may look familiar to many:

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In the above code, we've set up our API routes, but if you attempt to access them and are met with a 404 error, it means that something important is missing from your application setup.

The Solution

The good news is that the solution to your problem is relatively straightforward! Here’s what you need to do:

Step 1: Update Your Startup.cs File

You need to ensure that your application is configured to use controllers. This can be done by adding a line of code to the Configure method in your Startup.cs file. Specifically, you must include the following line:

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Why is This Step Necessary?

When you set up a new ASP.NET CORE project, certain configurations may not be automatically included, which leads to the issue of your API controllers not being recognized. By adding app.MapControllers(), you're instructing the application to map all attributes in your controllers to their appropriate endpoints.

Final Thoughts

After adding the app.MapControllers(); line to your Startup.cs, restart your application and attempt to access your API endpoint again. You should no longer see the 404 error, and your API should respond as expected.

Conclusion

Encountering a non-functional API controller in ASP.NET CORE 5 can be a hassle, but by ensuring you include app.MapControllers(); in your project configuration, you can resolve the issue quickly and efficiently. Always remember to double-check your setup when facing similar problems in the future.

Feel free to leave comments or ask questions below if you encounter any other issues while working with ASP.NET CORE. Happy coding!