docker-compose up failes: The current .NET SDK does not support targeting .NET Core 2.2

Question

I have .net core app which is dockerized Inside docker compose file bellow there are details of this container docker-compose up from windows cli produces following error

Step 11/20 : RUN dotnet restore My.Api/My.Api.csproj
 ---> Running in bc9d0ee76a7e
/usr/share/dotnet/sdk/2.1.202/Sdks/Microsoft.NET.Sdk/build/Microsoft.NET.TargetFrameworkInference.targets(135,5): error : The current .NET SDK does not support targeting .NET Core 2.2.  Either target .NET Core 2.0 or lower, or use a version of the .NET SDK that supports .NET Core 2.2. [/src/My.Api/My.Api.csproj]
ERROR: Service 'my.api' failed to build: The command '/bin/sh -c dotnet restore My.Api/My.Api.csproj' returned a non-zero code: 1

docker-compose.yml

version: '3.4'

networks:
    frontend:
    backend:

services:
    my.api:
        image: ${DOCKER_REGISTRY}myapi        
        build:
            context: .
            dockerfile: My.Api/Dockerfile  
        ports:
            - "5000:80"
        networks:
            - backend
            - frontend
        depends_on:
            - mssqlserver

    mssqlserver:
        image: "microsoft/mssql-server-linux:latest"
        .....

Dockerfile

FROM microsoft/aspnetcore:2.0 AS base
WORKDIR /app
EXPOSE 80

FROM microsoft/aspnetcore-build:2.0 AS build
WORKDIR /src

COPY My.Api/
RUN dotnet restore My.Api.csproj
COPY . .
WORKDIR /src/My.Api
RUN dotnet build My.Api.csproj -c Release -o /app

FROM build AS publish
RUN dotnet publish My.Api.csproj -c Release -o /app

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

dotnet --version

2.2.105

Update:

When I change Dockerfile to use microsoft/aspnetcore:2.2 instead of microsoft/aspnetcore:2.0 I'm getting

Step 1/20 : FROM microsoft/aspnetcore:2.2 AS base
ERROR: Service 'my.api' failed to build: manifest for microsoft/aspnetcore:2.2 not found

Answer 1

First, an important point:

The versions of .NET Core installed in Windows don't matter when it comes to a docker container. Whatever dotnet --version says in Windows doesn't matter. A docker container is a separate environment from your Windows environment. It actually runs a different userspace (Linux, not Windows). It can have a completely different set of programs and versions installed.

Now, going back, the error says:

error : The current .NET SDK does not support targeting .NET Core 2.2.  Either target .NET Core 2.0 or lower, or use a version of the .NET SDK that supports .NET Core 2.2

The last part of this error message is really important. It tells you the problem: you are using a .NET Core SDK (inside the docker container) that can not target 2.2.

(Remember that the version of .NET Core SDK that's normally installed in Windows is irrelevant for docker?)

So that version of the SDK are you using inside the docker container? Look at the Dockerfile again:

FROM microsoft/aspnetcore-build:2.0 AS build

You are using a .NET Core SDK that supports ASP.NET Core 2.0. In other words, you are using .NET Core SDK 2.0 and it only supports targetting .NET Core 2.0. You need to switch to an SDK that supports .NET Core 2.2.

Change FROM microsoft/aspnetcore:2.0 AS base to FROM microsoft/aspnetcore:2.2 AS base and FROM microsoft/aspnetcore-build:2.0 AS build to FROM microsoft/aspnetcore-build:2.2 AS build.

That will get you an SDK that lets you target .NET Core 2.2.

Edit: Ah, right. I missed something.

The Microsoft container images are described here. You need to use microsoft/dotnet:2.2-sdk for building (FROM microsoft/dotnet:2.2-sdk AS build) and microsoft/dotnet:2.2-aspnetcore-runtime for running (FROM microsoft/dotnet:2.2-aspnetcore-runtime as base).