F# REST API: A step by step using Entity Framework Core, MVC, and PostgreSQL
The objective of this tutorial is to spread the knowledge of the possibilities to use the traditional .NET Core libraries with F# very likely the way that they are used in C#, so you can take advantage of your previous knowledge about .NET core libraries and just care about learning the F# syntax.
Brief Introduction
One of the most popular ORM (Object-relational mapping) among the .NET core community is the Entity Framework Core, that distinguishes itself by:
- Being multi-platform;
- EF Core Supports more than one SQL provider: like the PostgreSQL, MySQL, SQLite and the obvious SQLServer;
- Having an in-memory storage system, that makes it possible to have a development environment without having a relational database set up for testing.
For this project, we are going to use .NET core 3.1, Visual Studio Code, Entity Framework Core, MVC Core, and a PostgreSQL database that will first be stored in memory, and later it will be hosted in AWS. The OS used in this tutorial is Ubuntu 18.04, but you can follow it with Windows or Mac OS, once that all software and extensions needed are multi-platform.
Let’s start to code
To start our project you need to open the terminal, choose one directory, and type the following commands:
dotnet new webapi -o FSToDoList -lang f#
code FSToDoListThe Visual Studio Code will open with the F# Web API .Net Core template, this template has already a default controller, and you can run it with these commands on the terminal embedded in VS Code:
dotnet restore
dotnet run
If you followed the tutorial so far, you could check your API running on https://localhost:5001/api/values
Now we can properly start to code, so first, let’s update project’s dependencies on the file FSToDoList.fsproj:
You must use the command dotnet restore in the embedded VS Code terminal to download all the project’s dependencies that were added.
Create two new folders: Data and Models.
Inside of the folder Models, you must create a new file and name it as ToDoItem.fs. In this file that will be added the model for the EF Core, bellow is the code that you will need:
Now, we need the data context for the project, so we will be able to retrieve the information from the database and work with the data collection on the HTTP requests. For that, just create a new file named ToDoContext.fs inside of the folder Data. Below is the code for this data context:
Create a new file in the folder Controllers and name it as ToDoItemsController.fs; It is in this file that the HTTP requests are going to be processed.
This demo project will manage the Get, Put, Post, and Delete requests. Here is the code for it:
The project is almost complete, just need to update the files Program.fs and Startup.fs to insert the EF Core service.
Well done! You just need to run the app by using the following command:
dotnet runGo to https://localhost:5001/api/todoitems, and you will see the items that are hardcoded in the temporary database.
To test the other functions, you can use an API testing software, e.g., curl or Postman.
Bonus: Add AWS support
You can use an Amazon RDS as the SQL provider for this project, to make this possible here are the steps needed:
- Create an AWS account if you don’t have one already.
- Go to your Management Console and search for RDS.
- Create a new Database and select PostgreSQL.
- Set up your database by setting up its template, name, and credentials
- Tip: to avoid a surprise bill, select the Free tier template.
Now you must update your appsettings.json to include the connection string to your AWS Postgres database, here’s to code to work over:
Then you need to update the file Startup.cs, first remove the line where the in-memory database is added and then replace it for this:
Note that the string inside of GetConnectionString must be the same as the name set as the identifier at appsettings.json.
