Hot Reload nearly always fails, with Blazor WebAssembly and "dotnet watch"

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Please get Hot Reload to work reliably and consistently with Blazor WebAssembly, especially with changes to .razor files. This feature seems so buggy when it should “just work”. It seems to work much better with non-Blazor server-side changes, e.g. to a Web API, but that’s not where much productivity benefit would result.

When using dotnet watch on my Server project, with verbose logging , I get watch : Hot reload capabilities: . (not even Baseline) and, on a change, No hot reload changes to apply. (when there are). This is with .NET 7.0.0 and SDK 7.0.100 on a solution that was created with .NET 6 and recently upgraded to 7.

Starting...
dotnet watch 🔥 Hot reload capabilities: .
dotnet watch ⌚ File changed: .\MySoln\Client\Shared\MainLayout.razor.
dotnet watch ⌚ No deltas modified. Applying changes to clear diagnostics.
dotnet watch ⌚ Received 1 from browser in [Count: 1, MessageType: Binary, EndOfMessage: True].
dotnet watch ⌚ No hot reload changes to apply.
dotnet watch 🔥 Hot reload change handled in 4092.6926ms.

When running from VS (with or without debugging), I get similar output: , or sometimes instead “Your debugged process might be corrupted and restarting it is recommended nearly always.”

The most relevant issue seems to be https://github.com/dotnet/aspnetcore/issues/40587, but there must be much more to that one that isn’t working right.

See also:

• https://github.com/dotnet/aspnetcore/issues/38029
• https://github.com/dotnet/aspnetcore/issues/38576
• https://github.com/dotnet/aspnetcore/issues/38809 (title says .cshtml but the same problem happens with .razor)
• https://github.com/dotnet/aspnetcore/issues/40587 and https://github.com/dotnet/sdk/pull/27699 (closed without fully fixing)
• https://github.com/dotnet/aspnetcore/issues/36723 (closed without fully fixing)
• https://github.com/dotnet/aspnetcore/issues/38561 (closed without fully fixing)
• https://github.com/dotnet/aspnetcore/issues/38036 (closed without fully fixing)
• https://developercommunity.visualstudio.com/t/blazor-hot-reload-not-working/1480369 (closed without fully fixing)
• https://github.com/dotnet/sdk/pull/23185 (closed as merged but no notice of what version it is fixed in)

Seems like there are a lot of others struggling too but not commenting in GitHub issues, e.g.

• https://www.reddit.com/r/Blazor/comments/10wwfpr/has_anyone_had_hotreload_randomly_stop_working/
• https://www.reddit.com/r/Blazor/comments/10kishh/blazor_united_prototype_for_from_steve_sanderson/j5r08b4/
• https://www.reddit.com/r/Blazor/comments/vaccxa/hot_reload_is_rubbish/
• https://stackoverflow.com/questions/69778272/unable-to-hot-reload-on-visual-studio-2022/74380447#74380447
• https://stackoverflow.com/questions/70005784/net-6-blazor-wasm-hot-reload-not-working/74750013
• https://learn.microsoft.com/en-us/answers/questions/908804/vs2022-blazor-server-app-hot-reload-notworking

Expected Behavior

• dotnet watch hot reload should just work. I don’t want to see “No hot reload changes to apply.”
• If it isn’t working and thus I get “watch : Hot reload capabilities: .”, I’d like to see output that tells me why in the verbose output (indeed, perhaps even in warnings).

.NET Version

7.0.0

Anything else?

dotnet --info

.NET SDK: Version: 7.0.100 Commit: e12b7af219

Runtime Environment: OS Name: Windows OS Version: 10.0.19044 OS Platform: Windows RID: win10-x64 Base Path: C:\Program Files\dotnet\sdk\7.0.100\

Host: Version: 7.0.0 Architecture: x64 Commit: d099f075e4

.NET SDKs installed: 5.0.408 [C:\Program Files\dotnet\sdk] 6.0.403 [C:\Program Files\dotnet\sdk] 7.0.100 [C:\Program Files\dotnet\sdk]

.NET runtimes installed: Microsoft.AspNetCore.App 3.1.25 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 6.0.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 7.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.NETCore.App 3.1.25 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 6.0.10 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 6.0.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 7.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.WindowsDesktop.App 3.1.25 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 6.0.10 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 6.0.11 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 7.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found: x86 [C:\Program Files (x86)\dotnet] registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables: Not set

[Stuart88]

Hot Reload is just terrible.

I feel bad criticising any of this because in the end it’s a ‘free’ framework that most of us haven’t helped to develop, but…

There is absolutely no point in allowing and/or promoting the existence of hot reload in its current state. It is rubbish, useless, pointless. Every little change (and sometimes no change at all) requires a rebuild. It isn’t ‘hot reload’ AT ALL.

[Contengo]

We have been working with Blazor for three years now, but are seriously contemplating switching everything to React solely because of this issue. The development experience is beyond painful - it would be better to switch the feature off and set the expectation that you always have to recompile. It’s the “waiting to see if it works, knowing it probably won’t” that kills all motivation and enthusiasm.