Diagnosing .NET Hot Reload Failures in JetBrains Rider

Recognizable condition

After saving a code change, the running application does not update. Rider shows no Hot Reload notification, no error dialog, and the Build window reports success. The application continues to behave as if the change was never applied.

Cause and diagnostic table

Possible cause	Typical symptom in Rider logs	How to verify
Project targets an unsupported .NET version (e.g., .NET Framework or .NET Core 3.1)	"Hot Reload not supported for this project type"	Check the project's TargetFramework in .csproj; Hot Reload requires .NET 5.0 or later.
Launch profile does not start a debug session (e.g., using dotnet run without debugging)	"Failed to acquire debug session"	Open the launch profile (Properties\launchSettings.json) and ensure the command uses dotnet with --no-build and the debugger attached.
Third‑party extension or custom MSBuild target interferes with the Hot Reload pipeline	Warnings about MSBuild Hot Reload targets being skipped	Temporarily disable extensions (via Settings → Plugins) and remove custom Import elements from the project file, then retry.
Hot Reload explicitly disabled in Rider settings	No Hot Reload log entries at all	Navigate to Settings → Build, Execution, Deployment → Hot Reload and verify the checkbox is enabled.

Ordered checks

1. Confirm project compatibility
   Open the .csproj file and verify that <TargetFramework>net5.0</TargetFramework> (or newer) is present. If the target is older, upgrade the project or accept that Hot Reload is unavailable.
2. Inspect the launch profile
   In Rider, open Run → Edit Configurations…, select the profile used to start the app, and check the Command line field. It should contain something like:

   dotnet run --no-build --project MyApp.csproj

   Ensure the Debug mode is selected (the debugger icon is active). If the profile uses dotnet run without debugging, switch to a debug configuration or add --debug where supported.
3. Enable Hot Reload in Rider settings
   Go to File → Settings → Build, Execution, Deployment → Hot Reload (Windows/Linux) or Rider → Preferences → … (macOS). Make sure Enable Hot Reload is checked. Click Apply and restart the IDE if prompted.
4. Review the Hot Reload log
   After making a trivial change (e.g., editing a string literal), open Help → Diagnostic Tools → Hot Reload log. Look for lines such as:
   • Hot Reload: patch applied
   • Hot Reload: skipped – reason: …
   If the log shows a skip reason, note it for the next step.
5. Test with a minimal project
   Create a new ASP.NET Core Web API project (dotnet new webapi -n TestHotReload) and run it via Rider’s default debug configuration. Apply a simple change (e.g., modify a returned string). If Hot Reload works here, the issue is specific to the original solution’s configuration or extensions.

Fixes tied to findings

• Unsupported .NET version – Update the TargetFramework to net5.0 or newer, reload the solution, and retry.
• Non‑debug launch profile – Edit the profile to launch with debugging (choose the .NET template that includes Attach debugger) or create a new debug configuration via Run → Edit Configurations → + → .NET Process.
• Hot Reload disabled – Enable the setting as described in step 3 of the ordered checks.
• Extension or MSBuild interference – Disable all third‑party plugins temporarily; if Hot Reload works, re‑enable them one by one to identify the culprit. For custom MSBuild targets, comment out any Import elements that reference Hot Reload and verify the build still succeeds.
• Persistent log skip reason – If the log indicates a specific blocker (e.g., Hot Reload not supported for project type: Azure Functions), consult Rider’s documentation for that project type; some project types require additional configuration or are not supported.

Escalation criteria

If after performing the checks above the application still does not reflect code changes:

1. Collect the Hot Reload log (Help → Diagnostic Tools → Hot Reload log) and the IDE log (Help → Diagnostic Tools → Show Log in Explorer).
2. Verify that the Rider version is 2022.3 or later (Help → About).
3. Create a minimal reproducible example (a new solution with only the problematic project) and attach the logs when submitting a request to JetBrains support or posting on the Rider community forums.

These steps give the support team the information needed to determine whether the failure is a configuration issue, a known limitation, or a bug requiring a fix.