Error: " The command could not be loaded, possibly because:" while trying to start a selenium docker container

Question

I want to execute my tests in docker and created 3 containers for it:

• chrome-node
• selenium-hub
• selenium.test

The first 2 container are running successfully, but im getting an error when the selenium.test container tries to start:

2024-02-27 16:16:10 The command could not be loaded, possibly because:
2024-02-27 16:16:10   * You intended to execute a .NET application:
2024-02-27 16:16:10       The application 'BitflySelenium.dll' does not exist.
2024-02-27 16:16:10   * You intended to execute a .NET SDK command:
2024-02-27 16:16:10       No .NET SDKs were found.
2024-02-27 16:16:10 
2024-02-27 16:16:10 Download a .NET SDK:
2024-02-27 16:16:10 https://aka.ms/dotnet-download
2024-02-27 16:16:10 
2024-02-27 16:16:10 Learn about SDK resolution:
2024-02-27 16:16:10 https://aka.ms/dotnet/sdk-not-found

I tried different approaches that i could find in google but im not able to find any solution.

My Dockerfile looks like this:

# Build stage
FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build-env
EXPOSE 80
EXPOSE 443
EXPOSE 4444

WORKDIR /app
COPY . .

RUN dotnet restore "BitflySelenium/BitflySelenium.csproj"
RUN dotnet build "BitflySelenium/BitflySelenium.csproj" -c Release

# Runtime stage
FROM mcr.microsoft.com/dotnet/aspnet:6.0
WORKDIR /app
COPY --from=build-env /app .
ENTRYPOINT ["dotnet", "BitflySelenium.dll"]

My docker-compose.yml looks like this:

version: '3.8'

services:
  selenium-hub:
    image: selenium/hub:4.1.2
    ports:
      - "4444:4444"

  chrome-node:
    image: selenium/node-chrome:4.1.2
    depends_on:
      - selenium-hub
    environment:
      - SE_EVENT_BUS_HOST=selenium-hub
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443

  selenium.test:
    build:
      context: .
      dockerfile: BitflySelenium/Dockerfile
    depends_on:
      - selenium-hub
    environment:
      - ASPNETCORE_ENVIRONMENT=Development

To start the container and creation of the images im using this command:

docker-compose up --build

This is just a personal project i use, just to improve my skills in selenium and docker. I chose the "Bitfly" website randomly.

I would appreciate any hints/help!

Answer 1

The error message indicates that dotnet is unable to find the .dll.

I created a minimal .Net application for testing.

├── BitflySelenium
│   ├── appsettings.Development.json
│   ├── appsettings.json
│   ├── BitflySelenium.csproj
│   ├── Controllers
│   │   └── WeatherForecastController.cs
│   ├── Dockerfile
│   ├── obj
│   │   ├── BitflySelenium.csproj.nuget.dgspec.json
│   │   ├── BitflySelenium.csproj.nuget.g.props
│   │   ├── BitflySelenium.csproj.nuget.g.targets
│   │   ├── project.assets.json
│   │   └── project.nuget.cache
│   ├── Program.cs
│   ├── Properties
│   │   └── launchSettings.json
│   └── WeatherForecast.cs
└── docker-compose.yml

I used your docker-compose.yml and made two minor tweaks to the Dockefile, being specific about the location of the output from dotnet build and then using that path in ENTRYPOINT.

FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build-env
EXPOSE 80
EXPOSE 443
EXPOSE 4444

WORKDIR /app
COPY . .

RUN dotnet restore "BitflySelenium/BitflySelenium.csproj"
# ⭐ Add the -o option here.
RUN dotnet build "BitflySelenium/BitflySelenium.csproj" -c Release -o build

FROM mcr.microsoft.com/dotnet/aspnet:6.0
WORKDIR /app
COPY --from=build-env /app .
# ⭐ Specify path to .dll here!
ENTRYPOINT ["dotnet", "build/BitflySelenium.dll"]

The .Net application doesn't do anything meaningful except run. With this setup you'll no longer get the errors you reported and you can add all of your application logic.