Deploy .Net Core App to Heroku

In this article, we will see how we can deploy .Net Core Apps to Heroku for free using docker.

As a developer, we love to do some side projects and sometimes we want to show it to our fellow coders or the rest of the world. In most cases, we run it locally and show it to our friends but what if we want to deploy it to the cloud, then we need some paid cloud services like Azure or AWS. But the thing is, most of the time our side project is just a POC and we don’t want to spend a penny on it, so in this scenario, Heroku comes to save the day.

.Net ❤️ Docker ❤️ Heroku

Things we need

1. .Net Core App
2. Docker
3. Visual Studio or VS Code
4. Heroku free account
5. Heroku CLI

Things to know

Heroku is a platform as a service (PaaS) that enables developers to build, run, and operate applications entirely in the cloud.

Currently, Heroku supports languages Ruby, Java, PHP, Python, Node, Go, Scala and Clojure but unfortunately not .Net or .Net Core. This where Docker comes into the picture. Heroku provides ways to deploy apps with Docker.

Containers are a standardized unit of software that allows developers to isolate their app from its environment, solving the “it works on my machine” headache. For millions of developers today, Docker is the de facto standard to build and share containerized apps — from desktop, to the cloud.

Let’s Start

Install Docker

If you don’t have Docker in your system make sure to install it first from Docker's official website.

Create a .Net Core App

We will create an ASP.Net Core 3.1 Web API application for this article. The default template comes with a WeatherForecastController it has nothing special just a plain controller with some endpoints. You can modify it you if like.

ASP.Net Core Web API

Next, we need a Dockerfile in the solution to add docker capabilities.

Create a Dockerfile next to csproj.

FROM mcr.microsoft.com/dotnet/core/aspnet:3.1-buster-slim AS base
WORKDIR /app
EXPOSE 80
EXPOSE 443
FROM mcr.microsoft.com/dotnet/core/sdk:3.1-buster AS build
WORKDIR /src
COPY ["./BlogDemo.csproj", "src/"]
RUN dotnet restore "src/BlogDemo.csproj"
COPY . .
WORKDIR "/src/"
RUN dotnet build "BlogDemo.csproj" -c Release -o /app/build
FROM build AS publish
RUN dotnet publish "BlogDemo.csproj" -c Release -o /app/publish
FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "BlogDemo.dll"]

You can visual studio to run the app but let’s do it with windows terminal or command prompt.

Run Locally

Using the terminal, change the directory to the location where csproj and Dockerfile resides.

-- Build docker image
docker build -t blogdemo .
-- Run docker image
docker run -d -p 5000:80 --name myapp blogdemo

Hit http://localhost:5000/weatherforecast in your browser and wow it’s running.

If till now everything is OK, it means we are ready to deploy it to the cloud.

Getting ready for the cloud

We need to modify Program.cs before publishing it to the cloud.

using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Threading.Tasks;
namespace BlogDemo
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }
public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.ConfigureKestrel(serverOptions =>
                    {
                        serverOptions.Listen(IPAddress.Any, Convert.ToInt32(Environment.GetEnvironmentVariable("PORT")));
                    }).UseStartup<Startup>();
                });
    }
}

We need to install Heroku-CLI that will help us to deploy images to Heroku.

Let's create an app on Heroku.

Heroku app creation

You can choose an appropriate app name. Here I am using my name for the app name.

If you browse to your app (https://vikas-sharma.herokuapp.com/). You will see a welcome screen.

Heroku App welcome screen

Now, it's time to deploy our API to Heroku.

We need to modify our Dockerfile before we can deploy it to the cloud.

Just change the last line of Dockerfile to —

CMD ["dotnet", "BlogDemo.dll"]

We need to login to Heroku via CLI. Open your terminal and get ready for some action.

Steps In Terminal:

1. Change directory to the location where csproj and Dockerfile resides.

2. Type below commands

heroku login

It will open the login page in the browser.

CLI login page

* heroku container:login
* docker login --username=_ --password=$(heroku auth:token) registry.heroku.com
* docker build -t registry.heroku.com/vikas-sharma/web .
* docker push registry.heroku.com/vikas-sharma/web
* heroku container:release web --app vikas-sharma

Here ‘vikas-sharma’ is the app name, you can replace it with your app name.

Now visit the URL: https://vikas-sharma.herokuapp.com/weatherforecast

App running on Heroku

And you are done!! The app is deployed and you can access it from anywhere. 😄

Final Words

It is very easier to deploy your apps to Heroku if you follow the steps correctly and after that, you can share your app with the world 🌏.

Happy Coding!!! 🤗