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Learn how to resolve issues with `.NET Core 3.1` routing when URLs without areas cause 404 errors, ensuring your application runs smoothly.
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This video is based on the question https://stackoverflow.com/q/68450852/ asked by the user 'JianYA' ( https://stackoverflow.com/u/4907861/ ) and on the answer https://stackoverflow.com/a/68451068/ provided by the user 'Yinqiu' ( https://stackoverflow.com/u/13973037/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting .NET Core 3.1 Routing: Fixing URLs Without Areas

In the world of ASP.NET Core development, routing is a crucial concept that determines how incoming requests are directed to the appropriate controller actions. However, it’s easy to run into issues, especially when dealing with areas and conventional route patterns. A common problem developers face is when URLs without areas fail to load correctly, resulting in 404 errors. In this guide, we will explore this issue and provide a clear solution to fix it.

Understanding the Problem

Let’s take a closer look at a scenario that illustrates this problem.

Imagine you have set up your routes in .NET Core 3.1 as follows:

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

In this configuration, the first route pattern is intended to handle URLs that incorporate areas. For example, a controller in the “Configuration” area might have a URL that looks like this: /Configuration/ApiKeyApplication/Index. This works perfectly and loads the page as expected.

However, if you create a controller without an assigned area, such as:

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

You may notice that attempting to access the URL /Confirm/ConfirmDetails can result in a frustrating 404 error.

Diagnosing the Root Cause

The issue lies in how the routing is configured for the ConfirmController. Since you’ve defined a custom route for this controller with "[Route("/[controller]")], this clashes with the default routing definition when you try to access the ConfirmDetails action using the standard route pattern.

Key Points

Routes defined with [Route] override conventional routing.

If the controller does not have a matching route set for the action, it results in a 404 error.

Implementing the Solution

To resolve this issue, you have two options:

Option 1: Remove the Route Attribute

The simplest solution is to delete the [Route("/[controller]")] attribute from the ConfirmController. By doing this, the conventional routing will take effect and your URLs will be resolved correctly:

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

Option 2: Modify the Route Attribute

If you still want to use route attributes for this controller but need to ensure that both the controller and action can be accessed, modify the route as follows:

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

With this change, the URL /Confirm/ConfirmDetails will properly map to the ConfirmDetails action, eliminating the 404 error.

Conclusion

Routing issues in ASP.NET Core can lead to broken URLs and 404 errors, but understanding how routes interact can help us troubleshoot effectively. By either removing custom route attributes or adjusting them for compatibility with your route patterns, you can ensure smooth navigation in your application.

Have you faced issues while configuring routing in your ASP.NET applications? Share your experiences in the comments below!