How to Deploy a .NET Core App to Heroku

Most developers and companies need a service provider to deploy their apps. There are many different ways to do so, however with Heroku it is simple and straightforward to deploy, manage,scale and configure an app. Heroku is a cloud computing service provider and supports many modern app languages for instance Python, Ruby, Java, and JavaScript. Unfortunately Heroku does not support .NET Core apps but there is a way to deploy a .NET Core application to Heroku through Docker.

Docker is a virtual machine which makes deployment of an app easier and efficient by using lightweight containers for all environments. A container accommodates all the dependencies required to run an applicaion.

Deploying a .NET Core app to Heroku has its prerequisites:

1. Docker for Windows
2. A Heroku account
3. Heroku CLI

After installing the prerequisites create a ASP.NET Core Web Application from Visual Studio 2019.

Create a new project by selecting ASP.NET Core Web Application

Give a Project name and create an app!

Start a project and when it is done and final (for now), add a docker file to the solution. Right click on the solution, then hover on Add and finally select Docker Support.

Click on Docker Support

When clicked on, Docker Support will add a Dockerfile. And if Docker is not running this message will pop-up.

Click Yes

Now go to the Dockerfile and configure the file as follows:

Default Dockerfile

This is the default Dockerfile when added to the solution. Now configure the Dockerfile. (F1SampleApp is the name of the solution)

FROM mcr.microsoft.com/dotnet/core/aspnet:3.1 AS base
WORKDIR /app
FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build
WORKDIR /src
COPY ["F1SampleApp.csproj", "F1SampleApp/"]
RUN dotnet restore "F1SampleApp/F1SampleApp.csproj"
WORKDIR "/src/F1SampleApp"
COPY . .
RUN dotnet build "F1SampleApp.csproj" -c Release -o /app/build
FROM build AS publish
RUN dotnet publish "F1SampleApp.csproj" -c Release -o /app/publish
FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
CMD ASPNETCORE_URLS=http://*:$PORT dotnet F1SampleApp.dll

This is how it should look like at the end

After this step go to your Heroku account and create a Heroku App.

Select Create new app

Give a App name (will be used during deployment) and choose a region

After the app created go to the project folder (not the solution folder, because Dockerfile is located in the project folder), open a powershell console and run the following command:

PS C:\Users\Hp\Desktop\f1project\F1SampleApp\F1SampleApp> docker build -t <docker-image-name> .

Be careful with the dot at the end. This command will build a docker image. If Docker is not running an error might occur.

This means that Docker is not running

If the command succeeds run the tag command to tag from source image into target image(on Heroku). Heroku app name is the app name when a Heroku App created.

PS C:\Users\Hp\Desktop\f1project\F1SampleApp\F1SampleApp> docker tag <docker-image-name> registry.heroku.com/<heroku-app-name>/web

Now that an image has been created, all that’s left is to deploy this image using Heroku CLI commands. First, login from PowerShell to Heroku.

PS C:\Users\Hp\Desktop\f1project\F1SampleApp\F1SampleApp> heroku login

This command will lead to a web page for verification after pressing any key. After verification run this command to login to the container.

PS C:\Users\Hp\Desktop\f1project\F1SampleApp\F1SampleApp> heroku container:login

Now push the container to Heroku.

PS C:\Users\Hp\Desktop\f1project\F1SampleApp\F1SampleApp> heroku container:push web -a <heroku-app-name>

Finally release the project to the web.

PS C:\Users\Hp\Desktop\f1project\F1SampleApp\F1SampleApp> heroku container:release web -a <heroku-app-name>

In the end test the results. Go to “<heroku-app-name>.herokuapp.com.” and see if the project is running.

Now a .NET Core application is deployed to Heroku.

Sources:

https://jakubwajs.wordpress.com/2020/01/31/deploying-asp-net-core-3-1-web-api-to-heroku-with-docker/

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