asp.net core docker-compose refresh on code changes

Question

I've read here that I can get possibility not to run docker-compose build every time code changes by adding volumes sections to docker-compose.yml. But I can't achieve this feature in my ASP.NET Core application. Dockerfile:

FROM microsoft/dotnet:2.1-aspnetcore-runtime AS base
WORKDIR /app
EXPOSE 80

FROM microsoft/dotnet:2.1-sdk AS build
WORKDIR /src
COPY ["dockercompose/dockercompose.csproj", "dockercompose/"]
RUN dotnet restore "dockercompose/dockercompose.csproj"
COPY . .
WORKDIR "/src/dockercompose"
RUN dotnet build "dockercompose.csproj" -c Release -o /app

FROM build AS publish
RUN dotnet publish "dockercompose.csproj" -c Release -o /app

FROM base AS final
WORKDIR /app
COPY --from=publish /app .
ENTRYPOINT ["dotnet", "dockercompose.dll"]

docker-compose.yml:

version: '3.4'

services:
  dockercompose:
    image: ${DOCKER_REGISTRY}dockercompose
    build:
      context: .
      dockerfile: dockercompose/Dockerfile
    ports:
     - "9000:80"
    volumes:
     - .:/src/dockercompose  

What am I missing?

Answer 1

You should use dotnet watch run for that. However that means you need to use the SDK image (microsoft/dotnet:2.1-sdk) not the runtime only image (microsoft/dotnet:2.1-aspnetcore-runtime).

I just use two Docker files and have two services defined in the docker-compose.yml. One uses the dockerfile with the runtime image (for deployment), the other one with the SDK image (for development).

The development dockerfile could look something like this:

FROM microsoft/dotnet:2.1-sdk AS build-env
# Use native linux file polling for better performance
ENV DOTNET_USE_POLLING_FILE_WATCHER 1
WORKDIR /app
ENTRYPOINT dotnet watch run --urls=http://+:5000

You might have to chnage the path according to your project and how you map it in your docker-compose.yml, but this is more or less it.