Docker Container for .NET Core

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Welcome back to .NET Core Central. Today I am going to write an introductory blog on docker containers. In this blog, I will create a sample .NET Core Console application and run in docker. Very basic implementation with just a Console.Write statement. In my future blogs, I will dig deeper into some complex implementation and running them in docker.

What is Docker Container?

Docker is a set of services that provides operating system-level virtualization. This virtualization helps deliver software in packages called containers. Containers are isolated from each other and extremely lightweight compared to virtual machines. Hence it is a perfect candidate for hosting microservices.

Docker Container Client for Windows 10

Windows 10 client for Docker is available for download at https://hub.docker.com/. SIgn-Up or Sign-in to download the client.

docker client

During installation, keep the default configuration to run as a Linux container, instead of a Windows container. This is to keep the container in line with the production environment.

Testing Docker Installation

Post-installation test and ensure Docker is installed properly.

Firstly, test docker images using command docker images

Secondly, to check the containers use the command docker ps -a

.NET Core Console Application

For creating a .NET Core Console application, open Visual Studio. I am using Visual Studio 2017. Firstly, click on New -> Project -> Console App (.Net Core).

new console application

Since this is an example to run in docker. Therefore, I will keep the default implementation of the Program.cs class. I will change the Console.Write statement with the string “Hello Docker World!”.

using System;

namespace Docker.Demo
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello Docker World!");
        }
    }
}

Creating a Docker image for the application

Before I can create a docker image, certainly, I will have to build the image. For building the docker image I will use the docker file. An example of that is available in https://docs.docker.com/engine/examples/dotnetcore/

Firstly, I will create a DockerFile for my solution.

FROM microsoft/dotnet:2.0-runtime AS base
WORKDIR /app

FROM microsoft/dotnet:2.0-sdk AS build
WORKDIR /src
COPY *.sln ./
COPY . /Docker.Demo/Docker.Demo.csproj /Docker.Demo/
RUN dotnet restore
COPY . .
WORKDIR /src/
RUN dotnet build -c Release -o /app

FROM build AS publish
RUN dotnet publish -c Release -o /app

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

Secondly, I will execute the following command to create the docker image docker build -t dockerdemo -f DockerFile .

Finally, I will verify if the image is created using the command docker images

docker image

Creating the container

Since the image is created, hence I will create a new container using the command docker create dockerdemo.

Since the image is created, therefore I will verify with command docker ps -a.

available containers

Finally, I will run the container using the command docker start -i cool_engelbart. Where cool_engelbart is the name of the container. And I am using the switch -i to run it in interactive mode. So that I can see the write statement.

console output

Conclusion

Running .NET Core application in docker is a breeze. Most importantly it integrates seamlessly. I will continue my exploration of docker and writing those experiences.

In addition, below is the complete YouTube video: https://youtu.be/6QiR0O5Irzs