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

[szalapski]

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 #40587, but there must be much more to that one that isn't working right.

See also:

• .NET 6 Blazor Hot Reload fails depending on the port specified for the application Url #38029
• Hotreload doesn't work on Blazor wasm (.NET6) #38576
• Hotreload not working with .cshtml files #38809 (title says .cshtml but the same problem happens with .razor)
• CLI Hot reload Blazor wasm just doesn't work. #40587 and Remove various timeouts sdk#27699 (closed without fully fixing)
• [dotnet-watch] Hot reload capabilities are sometimes not reported for blazor-wasm #36723 (closed without fully fixing)
• Blazor WASM Hot Reload cli not working #38561 (closed without fully fixing)
• Document How to Enable Hot Reloading Using dotnet run/watch #38036 (closed without fully fixing)
• https://developercommunity.visualstudio.com/t/blazor-hot-reload-not-working/1480369 (closed without fully fixing)
• Assume basline capabilities sdk#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.

[szalapski]

I don't feel bad, but I hope my criticism is constructive and optimistic. I want to help, too, but no idea how I can, as there is no clue as to what is wrong when Hot Reload fails.

For what it's worth, I wouldn't mind so much an automatic rebuild--my main concern in this issue is that I get No hot reload changes to apply. or Your debugged process might be corrupted and restarting it is recommended nearly always.

[MackinnonBuck]

Thanks for sharing this feedback. We are aware that there are a number of issues with hot reload we are trying to address. In order for us to address the issue you're facing, could you please provide a repro project hosted as a public GitHub repo that demonstrates the problem?

Hi @szalapski. We have added the "Needs: Author Feedback" label to this issue, which indicates that we have an open question for you before we can take further action. This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.

[danroth27]

@tmat @lambdageek

[danroth27]

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.

@szalapski Have you tried cleaning out the bin and obj folders and rebuilding?

[szalapski]

@danroth27 Yes, but I just tried it again to be sure. Deleted bin and obj in all three projects (Server, Client, Shared), and ran dotnet watch --project on the server project. No change:

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.

@MackinnonBuck, I'll try to get a example project up ASAP.

[szalapski]

@MackinnonBuck , here's the minimal example as requested.

https://github.com/szalapski/HotReloadIssue45519Demo

Clone this and run

dotnet watch --verbose --project ./TradeCars/Server

The site should start up. You'll see Hot reload capabilities: . which portends the failure. Edit anything in Index.razor to watch hot reload fail.

[mkArtakMSFT]

@tmat given the repro is provided, I'm assigning this to you to investigate. Thanks!