The evolution of the .NET ecosystem has brought several exciting tools that enhance the productivity of developers. One of the standout features in the latest versions of .NET is dotnet watch with Hot Reload improvements. In this blog, we’ll dive into how dotnet watch works, the recent Hot Reload improvements, and how these changes can significantly boost your development workflow.
What is dotnet watch?
dotnet watch is a command-line tool that monitors changes in your source code and automatically rebuilds and restarts your application. This tool helps developers by enabling faster feedback loops during development, as it eliminates the need to manually stop and restart your app every time you make a change to your code. It is primarily used in conjunction with ASP.NET Core or .NET Console applications to improve the speed and efficiency of development.
By running the dotnet watch command, developers can watch for changes in the project’s files and trigger rebuilds and restarts whenever code changes are detected. This is incredibly useful when you’re making frequent changes, as it saves time and effort and keeps you in the flow.
Example usage:
dotnet watch run
When running the above command, dotnet watch will automatically rebuild the application whenever it detects changes in the files within the project directory, thus helping you avoid the manual intervention needed to restart the application.
Enter Hot Reload
Hot Reload is a feature that allows you to apply code changes to a running application without having to stop, rebuild, or restart the application. It is a developer productivity feature that has been integrated into .NET through several updates and has been continuously improving over time. Instead of having to halt the application and rebuild the project each time you make changes, Hot Reload allows you to inject your changes directly into the running application, which drastically reduces downtime.
In earlier versions of .NET, Hot Reload capabilities were somewhat limited. However, with the latest updates, especially in .NET 6 and .NET 7, Microsoft has significantly improved the Hot Reload experience, enhancing developer workflows and making the feature more reliable and flexible.
Improvements in dotnet watch with Hot Reload
1. Seamless Code Changes with No Application Restart
Previously, developers would still have to restart their web application after making changes to certain parts of the code (like UI logic or component changes). With the latest Hot Reload improvements, the application now stays alive and continues to run as the changes are applied instantly. This means that UI changes, business logic changes, and even certain types of method modifications can now be reflected immediately.
For example, if you’re working on a Razor page or an MVC view, you can now make changes and see those reflected without reloading the page manually. This works even for more advanced scenarios, such as CSS or JavaScript changes in Blazor applications.
2. Faster Feedback Loop with Hot Reload
Before, dotnet watch would perform a complete rebuild and restart every time you made a change to the source code. The rebuild process, especially for larger projects, could introduce a lot of friction in the development process. Now, with Hot Reload improvements, dotnet watch only reloads the affected parts of the application—this results in faster feedback and a more agile development process.
If you make a small change in a method or class, the Hot Reload system identifies exactly what needs to be updated and applies the changes directly without reloading everything. This greatly reduces the waiting time, especially in larger applications.
3. Better Support for Non-UI Code Changes
One of the most impressive aspects of the Hot Reload improvements in .NET is the ability to apply changes to non-UI code while the application is running. This includes making changes to services, business logic, and even methods in the backend layers of your application.
Previously, Hot Reload was mostly focused on UI changes, but now it works more comprehensively across the application. You can edit code that doesn’t directly affect the UI, like backend services, APIs, or even data models, and see the results of those changes immediately.
4. Cross-Platform Hot Reload
Another major enhancement is the cross-platform support for Hot Reload. This means that Hot Reload now works seamlessly across Windows, Linux, and macOS, making it a viable tool for a broader range of .NET developers working on various operating systems.
For developers using .NET for building cross-platform applications (such as those targeting macOS or Linux), this improvement ensures that the Hot Reload feature works consistently across different environments, providing the same seamless experience as on Windows.
5. Improved Debugging Experience
Hot Reload now also integrates better with the debugging process. If you’re debugging your application, you no longer need to stop and restart the debugger every time you make a code change. You can simply apply the changes while the debugger is running, and the application will continue running with the new code.
This reduces the need for lengthy reinitializations, particularly in scenarios where debugging sessions are time-consuming or complex. It allows developers to maintain their debugging sessions while they iteratively improve their code.
6. Support for Blazor Applications
Blazor, Microsoft’s web framework for building interactive UIs using C#, benefits significantly from the Hot Reload improvements. You can make changes to the Razor components and immediately see the updated UI in the browser without needing to refresh the page.
Blazor developers previously had to rely on the traditional hot-reload (which was not as powerful) or use an inefficient full rebuild process. With Hot Reload improvements, Blazor apps can now reflect changes much faster, streamlining the development experience.
How to Use dotnet watch with Hot Reload
Prerequisites
- .NET 6 or later
- Supported development environment (Visual Studio, Visual Studio Code, or CLI)
How to Enable Hot Reload
To start using Hot Reload, you simply need to use the dotnet watch command with the appropriate application.
- For ASP.NET Core Web Applications:
dotnet watch run - For Console Applications:
dotnet watch --no-launch-profile - For Blazor Applications:
dotnet watch run
When you run these commands, your changes will be automatically applied to the running application, and you’ll see them reflected in real-time without needing to restart the application.
Additional Options
You can customize the behavior of dotnet watch by using several options:
--filter <glob>: Allows you to specify which files to watch (e.g.,--filter "src/**/*.cs").--no-launch-profile: Ensures that no default profile is used when running the app.--verbose: Outputs detailed logs that help with debugging issues.
Conclusion
The dotnet watch tool combined with Hot Reload improvements has revolutionized how .NET developers work. By providing faster feedback loops, better support for non-UI code changes, and seamless integration with debugging workflows, developers can now focus more on writing and improving their code rather than managing the development environment.
These improvements significantly enhance productivity, reduce waiting times, and offer a much more enjoyable development experience. Whether you’re building web applications with ASP.NET Core, developing console apps, or experimenting with Blazor, dotnet watch with Hot Reload is now an indispensable tool for modern .NET development.