{"id":89245,"date":"2020-12-07T16:05:06","date_gmt":"2020-12-07T16:05:06","guid":{"rendered":"https:\/\/www.red-gate.com\/simple-talk\/?p=89245"},"modified":"2022-04-24T21:25:22","modified_gmt":"2022-04-24T21:25:22","slug":"creating-your-first-crud-app-with-suave-and-f","status":"publish","type":"post","link":"https:\/\/www.red-gate.com\/simple-talk\/development\/dotnet-development\/creating-your-first-crud-app-with-suave-and-f\/","title":{"rendered":"Creating your first CRUD app with Suave and F#"},"content":{"rendered":"

F# is the go-to language if you\u2019re seeking functional programming within the .NET world. It is multi-paradigm, flexible, and provides smooth interoperability with C#, which brings even more power to your development stack, but did you know that you can build APIs with F#? Not common, I know, but it\u2019s possible due to the existence of frameworks like Suave.io<\/a>.<\/p>\n

Suave is a lightweight, non-blocking web server. Since it is non-blocking, it means you can create scalable applications that perform way faster than the ordinary APIs. The whole framework was built as a non-blocking organism.<\/p>\n

Inspired by Happstack<\/a>, it aims to embed web server capabilities into applications by providing support to components and services like Websockets, HTTPS, multiple TCP\/IP bindings, Basic Access Authentication, Keep-Alive, HTTP compression, and many more.<\/p>\n

In this article, you\u2019ll be driven through the Suave server by developing a complete CRUD REST API.<\/p>\n

Setting Up<\/h2>\n

Suave can be installed via NuGet Manager. However, before you can do it, you need to create a project in your Visual Studio Community Edition.<\/p>\n

First, make sure you have the .NET Core SDK installed. If not, go ahead and install it<\/a>.<\/p>\n

Then, open Visual Studio, go to the \u201cCreate a new project\u201d window, and filter for F# applications, and select the option \u201cConsole App (.NET Core)\u201d as shown in Figure 1. Click Next<\/em>.<\/p>\n

<\/p>\n

Figure 1.<\/strong> Creating a new F# project.<\/p>\n

The following window will ask for a project and solution name, as well as the folder destination. Fill the fields according to Figure 2 and click Create<\/em>. <\/p>\n

Figure 2.<\/strong> Providing a project and solution name.<\/p>\n

Once the project creation finishes, you\u2019ll be able to see that only one file comes with it: the Program.fs<\/em>. Within it, there\u2019s a Hello World example in F#.<\/p>\n

That\u2019s a very basic structure of an F# program, but this example won\u2019t use any of it.<\/a><\/p>\n

Installing Suave<\/h2>\n

Before going any further, you need to set up Suave properly. The usual method<\/a> recommends doing it via Paket<\/a>, however, since you\u2019re already within the Visual Studio environment, stick to NuGet.<\/p>\n

Right-click the solution and select \u201cManage NuGet Packages for Solution…\u201d and browse for Suave at the search box.<\/p>\n

Select it according to Figure 3 and click the Install<\/em> button.<\/p>\n

<\/p>\n

Figure 3.<\/strong> Installing Suave at NuGet.<\/p>\n

For the API construction, you\u2019ll also need Newtonsoft\u2019s JSON package, as it provides a handful of auxiliary methods to deal with conversions from object to JSON and vice versa.<\/p>\n

Follow Figure 4 instructions to install it.<\/p>\n

<\/p>\n

Figure 4.<\/strong> Installing Newtonsoft.Json dependency.<\/p>\n

The Project Structure<\/h2>\n

Great! Now move on to the project building. You noticed that you already have a Program.fs<\/em> file. You\u2019ll use it as the main execution file. However, two other files are needed: one for the in-memory database operations, and the other for the service operations.<\/p>\n

Go ahead and create both of them according to Figures 5 and 6 below.<\/p>\n

<\/p>\n

Figure 5.<\/strong> Creating the user\u2019s repository.<\/p>\n

<\/p>\n

Figure 6.<\/strong> Creating the user\u2019s service.<\/p>\n

The Repository<\/h2>\n

First, start coding the repository since it\u2019s the basis for the rest of the API. Take the code from Listing 1 and paste it into the UserRepository.fs<\/em> file.<\/p>\n

Listing 1.<\/strong> The user\u2019s repository code.<\/p>\n

namespace SuaveAPI.UserRepository\r\nopen System.Collections.Generic\r\ntype User =\r\n    { UserId: int\r\n      Name: string\r\n      Age: int\r\n      Address: string\r\n      Salary: double }\r\nmodule UserRepository =\r\n    let users = new Dictionary<int, User>()\r\n    let getUsers () = users.Values :> seq<User>\r\n    let getUser id =\r\n        if users.ContainsKey(id) then Some users.[id] else None\r\n    let createUser user =\r\n        let id = users.Values.Count + 1\r\n        let newUser = { user with UserId = id }\r\n        users.Add(id, newUser)\r\n        newUser\r\n    let updateUserById id userToUpdate =\r\n        if users.ContainsKey(id) then\r\n            let updatedUser = { userToUpdate with UserId = id }\r\n            users.[id] <- updatedUser\r\n            Some updatedUser\r\n        else\r\n            None\r\n    let updateUser userToUpdate =\r\n        updateUserById userToUpdate.UserId userToUpdate\r\n    let deleteUser id = users.Remove(id) |> ignore<\/pre>\n
For the sake of simplicity, this project won\u2019t make use of any physical database, so the user\u2019s data will be stored in an in-memory Dictionary called users.<\/p>\n
The dictionary\u2019s keys refer to each user\u2019s id, while the values represent the user objects.<\/p>\n
The full repository is made of six main operations:<\/p>\n