Containerizing .NET 8 Blazor WASM breaks after update from .NET 6

Question

After updating the .NET Version from 6 to 8 i can't use the deployed WebApp after starting the container and get the Exception shown down below

I have this Dockerfile now, which worked fine with .NET 6. It just differs in the SDK Version.

Dockerfile

FROM node:21-alpine3.18 as build-npm
WORKDIR /src`
COPY ["MyProj", "MyProj"]
WORKDIR /src/MyProj/NpmJS/
RUN npm install
RUN npm run build

FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
WORKDIR /src
COPY --from=build-npm /src .
COPY ["otherProj", "otherProj"]
RUN dotnet restore "MyProj/MyProj.csproj"

FROM build AS publish
ENV BuildingDocker true
RUN dotnet publish "MyProj/MyProj.csproj" -c Release --no-restore -o /app/publish

FROM nginx:alpine AS final
WORKDIR /usr/share/nginx/html
COPY --from=publish /app/publish/wwwroot .
COPY MyProj/nginx.conf /etc/nginx/nginx.conf

Steps To Reproduce

Obviously you gonna need .NET 8 Workloads and Docker installed and running.

1. Create Blazor-WebAssembly App Project with .NET 8
2. Adjust your launchsettings.json in the Projects/Properties Folder and set:

"applicationUrl": "https://localhost:5001;http://localhost:5000"

3. Use this Dockerfile as u wont need the NPM Part :

FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
WORKDIR /src
COPY --from=build-npm /src .
COPY ["otherProj", "otherProj"]
RUN dotnet restore "MyProj/MyProj.csproj"

FROM build AS publish
ENV BuildingDocker true
RUN dotnet publish "MyProj/MyProj.csproj" -c Release --no-restore -o /app/publish

FROM nginx:alpine AS final
WORKDIR /usr/share/nginx/html
COPY --from=publish /app/publish/wwwroot .
COPY MyProj/nginx.conf /etc/nginx/nginx.conf

4. Create nginx.conf in Project root:

events { }
http {
include mime.types;
server {
listen 5001;

    location / {
        root /usr/share/nginx/html;
        try_files $uri $uri/ /index.html =404;
    }
}
}

5. Build dockerfile with : docker build -t MyApp .
6. I start it via compose file but this command should do it for single proj: docker run MyApp -p 5001:5001

Navigate to localhost and Open Dev Tools

See following Error:

Uncaught TypeError: Cannot read properties of undefined (reading 'dotnet.wasm')
at blazor.webassembly.js:1:35948
at window.wasmmodulecallback (blazor.webassembly.js:1:42668)
at :1:20
at blazor.webassembly.js:1:43463
at blazor.webassembly.js:1:43478
at new Promise ()
at Object.start (blazor.webassembly.js:1:34639)
at Object.At [as start] (blazor.webassembly.js:1:59571)

Any help or guidance appreciated.

I had this Error on .NET Update locally in my Browser too. Clearing the Cache Storage fixed it but not for this Issue.

Answer 1

This error is because some packages are not get upgraded. After change the project version, you could try delete .bin .obj folder and rebuild.
Or if it doesn't work, create a new .Net8 project and copy your old files into it will solve the problem.