Software⏱️ 3 min read📅 2026-06-03

How to Fix: 500 Error when setting up Swagger in asp .net CORE / MVC 6 app

Learn how to fix: 500 Error when setting up Swagger in asp .net CORE / MVC 6 app.

Quick Answer: Try checking your system settings or restarting.

📋 Table of Contents

  1. 🛑 Root Causes of the Error
  2. 🚀 How to Resolve This Issue
  3. 💡 Conclusion

The Swagger UI is experiencing a 500 error when trying to generate API documentation in an ASP.NET Core/MVC 6 project. This issue typically occurs due to incorrect configuration or missing dependencies.

To resolve this issue, ensure that the Swashbuckle NuGet package is installed and properly configured in the project. Check the Swagger document options for any typos or formatting issues.

🛑 Root Causes of the Error

  • A common cause of this error is an incorrect or missing configuration file (e.g., `appsettings.json` or `config.cs`). Verify that these files are correctly formatted and contain all necessary dependencies.
  • Another possible cause is a mismatch between the Swagger document version and the API version being documented. Ensure that the versions match to avoid conflicts.

🚀 How to Resolve This Issue

Correctly configure the Swagger document options

  1. Step 1: Add the `using Swashbuckle.SwaggerGen;` statement to the project file (e.g., `Startup.cs`).
  2. Step 2: Update the `ConfigureServices` method in the `Startup.cs` file to include the correct configuration for Swagger document generation.
  3. Step 3: Ensure that the `appsettings.json` or `config.cs` file contains the necessary dependencies, such as the Swashbuckle NuGet package.

Check for any typos or formatting issues in the Swagger document options

  1. Step 1: Review the Swagger document options to ensure that there are no typos or formatting errors.
  2. Step 2: Verify that the `SingleApiVersion` and `Info` properties are correctly configured.

💡 Conclusion

To resolve the 500 error when setting up Swagger in an ASP.NET Core/MVC 6 project, carefully review the configuration options and dependencies. Ensure that all necessary NuGet packages are installed and properly configured to avoid conflicts.

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