9. Running Your First ASP.NET Core Application

In the previous article, we thoroughly discussed the structure of an ASP.NET Core project. In this one, we’ll learn how to run our first ASP.NET Core application and perform some basic tests. By completing this tutorial, you’ll be able to launch your application and see it running in a web browser.

1. Prerequisites

Ensure you’ve installed the required environment—specifically the .NET SDK and an IDE (e.g., Visual Studio or Visual Studio Code)—as instructed in the previous article. First, verify that your command-line terminal is currently located in the directory where you created your project.

2. Running Your ASP.NET Core Application

From your project directory, open a command-line tool and execute the following command:

dotnet run

Application Output

After running the command, you’ll see output similar to the following:

Now listening on: http://localhost:5000
Application started. Press Ctrl+C to shut down.

This indicates that your application has successfully started and is listening for HTTP requests at http://localhost:5000. At this point, open your web browser and navigate to that address—you should see the default welcome page.

Troubleshooting Common Issues

If you encounter issues—for example, if port 5000 is already in use—you can either modify the port configuration in the launchSettings.json file or specify an alternative URL directly via the command line:

dotnet run --urls "http://localhost:5001"

3. Running the Application in Visual Studio

If you’re using Visual Studio as your IDE, follow these steps to run the application:

1. Ensure your project is selected in Solution Explorer.
2. Click the green “Play” (Start) button on the toolbar.
3. Visual Studio will automatically launch your default browser and display the running application.

Configuring Startup Options

You can customize startup behavior—including the default launch URL and environment variables—via your project’s Properties window. This provides greater flexibility when configuring how your application runs during development.

4. Testing the Application

Navigate to http://localhost:5000 (or whichever port you configured) in your browser. You should see the default welcome page:

This confirms that you’ve successfully created and launched your ASP.NET Core application.

5. Hot Reload Support

During development, ASP.NET Core supports hot reload, enabling you to view code changes instantly—without restarting the application. Make sure you’re using an IDE that supports hot reload (e.g., Visual Studio 2022 or Visual Studio Code with the C# extension), and ensure hot reload is enabled while your app is running.

For example, try modifying the "Hello World" string in Startup.cs (or Program.cs, depending on your project template), then save the file. The change will appear immediately in your browser—no manual refresh required.

6. Next Steps

You’ve now successfully built and run your first ASP.NET Core application! Next, we’ll dive deeper into handling HTTP requests and responses—and explore how to configure routing and middleware. In the upcoming article, we’ll cover “Routing and Middleware: Understanding Routing”, laying the foundation for understanding ASP.NET Core’s request-processing pipeline.

By completing these steps, you’ve built and launched an ASP.NET Core application from scratch—establishing a solid foundation for your future development journey. Keep exploring new technologies—and see you in the next article!