Using Visual Studio 2022 Hot Reload to Edit .NET Code Without Restarting

Problem: Losing development flow when a tiny code change forces a restart

When you are debugging a .NET application, even a small edit—such as tweaking a string returned by an API endpoint—often requires stopping the debugger, rebuilding, and launching again. This interrupts the feedback loop and can slow down iterative work, especially when you are fine‑tuning UI logic or experimenting with algorithm changes.

Thesis: Visual Studio 2022’s Hot Reload lets you apply many intra‑method edits to a running .NET process, preserving the debugging session while providing immediate feedback.

How Hot Reload works

Hot Reload relies on the Edit and Continue (EnC) infrastructure built into the .NET runtime. When you make a change that the runtime can reinterpret—like editing the body of a method, an async method, or a property initializer—Visual Studio sends a lightweight payload to the attached process. The runtime patches the existing IL in place, updates the stack frames, and continues execution. A blue dot appears on the edited line and a banner confirms the change was applied.

If the edit touches the method signature, adds or removes a type, or modifies the project’s dependency graph, the runtime cannot safely patch the existing code. In those cases Visual Studio shows a prompt to restart the debugger.

Supported edits and limitations

• Supported: method bodies, async/await blocks, property initializers, field initializers, changes inside lambda expressions.
• Not supported: renaming a method or type, changing method signatures (parameters, return type, accessibility), adding/removing types, modifying attributes that affect the type layout, editing native code or mixed‑mode C++/CLI assemblies.
• Project types: ASP.NET Core, WPF, Windows Forms, console apps targeting .NET 6+ when launched with debugging (F5) or without debugging (Ctrl+F5).
• Prerequisite: Edit and Continue must be enabled under Debug → Options → General → Enable Edit and Continue. If disabled, Hot Reload silently ignores edits.

Worked example: Editing an ASP.NET Core Web API controller

Follow these steps in Visual Studio 2022 (version 17.0 or later). No special permissions are required beyond the ability to create and run a project.

1. Create a new ASP.NET Core Web API project (File → New → Project → ASP.NET Core Web API).
2. Press F5 to start debugging. The app launches and the debugger attaches.
3. Open Controllers/WeatherForecastController.cs and locate the Get method.
4. While the app is running, change the return string from "Hello World" to "Hello from Hot Reload" inside the method body.
5. Observe the editor: a blue dot appears on the edited line and a banner reads “Hot Reload applied”.
6. In a browser or using curl, call the endpoint again (GET https://localhost:{port}/weatherforecast). The response now contains the new string without stopping the debugger.

// Before edit
return new string[] { "Hello World" };

// After edit (applied via Hot Reload)
return new string[] { "Hello from Hot Reload" };

Verification steps

To confirm Hot Reload is active, you can:

• Look for the blue dot on the edited line and the notification banner at the top of the editor.
• Make a change that is known to be unsupported (e.g., rename the Get method to GetData). Visual Studio will display a dialog stating “The following changes require a restart”.
• Disable Edit and Continue (Debug → Options → General → uncheck Enable Edit and Continue), repeat a supported edit, and notice that no blue dot appears and the change is not reflected until you restart.

Trade‑offs and when to avoid Hot Reload

Hot Reload is excellent for rapid experimentation, but it is not a substitute for a full rebuild in all scenarios:

• If you need to update a data model, add a new service, or change a constructor signature, you must stop and restart.
• When using profilers, IntelliTrace, or native debuggers that attach to the process, the EnC mechanism is disabled, so Hot Reload will not work.
• Projects targeting .NET Framework or containing mixed‑mode C++/CLI assemblies fall back to the traditional edit‑compile‑debug cycle.

Understanding these limits helps you decide when to rely on Hot Reload and when to plan a restart.

Closing: Keep the feedback loop tight

By enabling Edit and Continue and staying within the supported edit boundaries, you can use Visual Studio 2022’s Hot Reload to see the impact of code changes instantly, preserving your debugging session and reducing context switches. Try the example above, verify the blue dot and banner, and incorporate Hot Reload into your daily workflow for faster iterative development.