Minimal API Swagger doc keeps returning 404 when published to IIS? Don’t Panic! We’ve Got You Covered!

Are you tired of dealing with the frustration of a Minimal API Swagger doc that returns a 404 error when published to IIS? You’re not alone! Many developers have encountered this issue, and it’s more common than you think. In this article, we’ll guide you through the possible causes and provide step-by-step solutions to get your Swagger doc up and running in no time.

What’s Causing the 404 Error?

Before we dive into the fixes, let’s take a closer look at some possible reasons why your Minimal API Swagger doc is returning a 404 error:

• Incorrect Swagger configuration: Misconfigured Swagger settings can lead to a 404 error. Make sure you’ve correctly set up your Swagger middleware and enabled Swagger UI.
• IIS configuration issues: Inconsistent or incorrect IIS settings can also cause a 404 error. Double-check your IIS configuration to ensure it’s set up correctly for your Minimal API.
• Route conflicts: Conflicting routes in your API can prevent the Swagger doc from functioning correctly. Review your route configurations to identify any potential conflicts.
• Missing dependencies: Failing to include required dependencies or nuget packages can result in a 404 error. Verify that you’ve installed all necessary packages for your Minimal API.

Solution 1: Verify Swagger Configuration

Let’s start by reviewing your Swagger configuration:

builder.Services.AddSwaggerGen(c =>
{
    c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API", Version = "v1" });
});

In the above code, we’re adding SwaggerGen to the service collection and configuring a single Swagger document called “v1”. If you’re using a different version or configuration, adjust the code accordingly.

Next, make sure you’ve enabled Swagger UI in your Minimal API:

app.UseSwaggerUI(c =>
{
    c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
});

In this example, we’re configuring Swagger UI to point to our “v1” Swagger document. Adjust the endpoint URL to match your Swagger document’s configuration.

Step-by-Step Instructions

1. In your Minimal API project, open the Program.cs file.
2. Review the Swagger configuration code to ensure it matches the above examples.
3. Verify that you’ve enabled Swagger UI and configured the correct endpoint URL.
4. Save the changes and rebuild your project.
5. Publish your Minimal API to IIS again.

Solution 2: Review IIS Configuration

If Solution 1 doesn’t resolve the issue, let’s take a closer look at your IIS configuration:

Here are some common IIS configuration mistakes that might cause a 404 error:

• Incorrect application pool settings: Ensure the application pool is set to the correct .NET Framework version and pipeline mode.
• Mismatched IIS site bindings: Verify that the IIS site bindings match the URL and port number used in your Minimal API.
• Inconsistent web.config settings: Review your web.config file to ensure it’s configured correctly for your Minimal API.

Step-by-Step Instructions

1. Open IIS Manager and select your Minimal API site.
2. Verify the application pool settings, ensuring the correct .NET Framework version and pipeline mode.
3. Check the site bindings to ensure they match the URL and port number used in your Minimal API.
4. Review the web.config file to ensure it’s configured correctly for your Minimal API.
5. Save any changes made and restart the IIS site.

Solution 3: Resolve Route Conflicts

Route conflicts can be a common issue in Minimal APIs. Let’s investigate and resolve any potential conflicts:

Here are some steps to identify and resolve route conflicts:

• Review route configurations: Verify that you haven’t accidentally defined duplicate or conflicting routes in your Minimal API.
• Use route debugging tools: Utilize route debugging tools, such as the .NET CLI or third-party libraries, to identify and diagnose route conflicts.
• Rename conflicting routes: Rename any conflicting routes to ensure they’re unique and don’t overlap.

Step-by-Step Instructions

1. In your Minimal API project, review the route configurations to identify any potential conflicts.
2. Use route debugging tools to diagnose and visualize your routes.
3. Rename any conflicting routes to ensure they’re unique and don’t overlap.
4. Save the changes and rebuild your project.
5. Publish your Minimal API to IIS again.

Solution 4: Verify Dependencies and NuGet Packages

Finally, let’s ensure you’ve installed all the necessary dependencies and NuGet packages for your Minimal API:

Here are the essential dependencies and NuGet packages required for Swagger to work in a Minimal API:

• Microsoft.AspNetCore.Mvc.Versioning
• Swashbuckle.AspNetCore
• Microsoft.OpenApi

Step-by-Step Instructions

1. In your Minimal API project, open the .csproj file.
2. Verify that the above dependencies and NuGet packages are installed and up-to-date.
3. If any packages are missing, install them using the NuGet package manager.
4. Save the changes and rebuild your project.
5. Publish your Minimal API to IIS again.

Conclusion

By following these solutions and step-by-step instructions, you should be able to resolve the 404 error issue with your Minimal API Swagger doc when published to IIS. Remember to:

• Verify Swagger configuration and enable Swagger UI.
• Review IIS configuration for potential mistakes.
• Identify and resolve route conflicts.
• Verify dependencies and NuGet packages are installed and up-to-date.

If you’ve reached this point and still encounter issues, consider additional troubleshooting steps or seek guidance from the developer community.

Solution	Description
1	Verify Swagger configuration and enable Swagger UI.
2	Review IIS configuration for potential mistakes.
3	Identify and resolve route conflicts.
4	Verify dependencies and NuGet packages are installed and up-to-date.

By applying these solutions and following the step-by-step instructions, you’ll be well on your way to resolving the 404 error issue with your Minimal API Swagger doc when published to IIS. Happy coding!

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