A functional ASP.NET Core micro framework for building rich web applications.

Read this blog post on functional ASP.NET Core for more information.

This project has been fairly stable for a while now and will be entering a beta phase relatively soon. Bigger API changes are less frequent now.

Giraffe was formerly known as ASP.NET Core Lambda and has been recently renamed to better distinguish from AWS Lambda as well as establish a more unique brand.

The old NuGet package has been unlisted and will not receive any updates any more. Please use the new NuGet package Giraffe going forward.

• About
• Basics
  • HttpHandler
  • Combinators
    • bind (>>=)
    • compose (>=>)
    • choose
• Default HttpHandlers
  • choose
  • GET, POST, PUT, PATCH, DELETE
  • mustAccept
  • challenge
  • signOff
  • requiresAuthentication
  • requiresRole
  • requiresRoleOf
  • clearResponse
  • route
  • routef
  • routeCi
  • routeCif
  • routeStartsWith
  • routeStartsWithCi
  • subRoute
  • subRouteCi
  • setStatusCode
  • setHttpHeader
  • setBody
  • setBodyAsString
  • text
  • json
  • xml
  • negotiate
  • negotiateWith
  • htmlFile
  • dotLiquid
  • dotLiquidTemplate
  • dotLiquidHtmlView
  • razorView
  • razorHtmlView
  • renderHtml
  • warbler
• Custom HttpHandlers
• Model Binding
  • bindJson
  • bindXml
  • bindForm
  • bindQueryString
  • bindModel
• Installation
• Sample applications
• Benchmarks
• Building and developing
• Contributing
• Contributors
• License

Giraffe is an F# web framework similar to Suave, but has been designed with ASP.NET Core in mind and can be plugged into the ASP.NET Core pipeline via middleware. Giraffe has been heavily inspired by Suave and its concept of web parts and the ability to compose many smaller web parts into a larger web application.

If you'd like to learn more about the motivation of this project please read this blog post on functional ASP.NET Core.

Giraffe is intended for developers who want to build rich web applications on top of ASP.NET Core in a functional first approach. ASP.NET Core is a powerful web platform which has support by Microsoft and a huge developer community behind it and Giraffe is aimed at F# developers who want to benefit from that eco system.

It is not designed to be a competing web product which can be run standalone like NancyFx or Suave, but rather a lean micro framework which aims to complement ASP.NET Core where it comes short for functional developers at the moment. The fundamental idea is to build on top of the strong foundation of ASP.NET Core and re-use existing ASP.NET Core building blocks so F# developers can benefit from both worlds.

You can think of Giraffe as the functional counter part of the ASP.NET Core MVC framework.

The only building block in Giraffe is a so called HttpHandler:

type HttpHandlerContext =
    {
        /// ASP.NET Core HttpContext
        HttpContext : HttpContext

        /// Service Locator to retrieve registered services on demand
        Services    : IServiceProvider

        /// Default logger
        Logger      : ILogger
    }

type HttpHandlerResult = Async<HttpHandlerContext option>

type HttpHandler = HttpHandlerContext -> HttpHandlerResult

A HttpHandler is a simple function which takes in a HttpHandlerContext and returns an object of the same type (wrapped in an option and async workflow) when finished.

Inside that function it can process an incoming HttpRequest and make changes to the HttpResponse of the given HttpContext. By receiving and returning a HttpContext there's nothing which cannot be done from inside a HttpHandler.

A HttpHandler can decide to not further process an incoming request and return None instead. In this case another HttpHandler might continue processing the request or the middleware will simply defer to the next RequestDelegate in the ASP.NET Core pipeline.

The core combinator is the bind function which you might be familiar with:

let bind (handler : HttpHandler) =
    fun (result : HttpHandlerResult) ->
        async {
            let! ctx = result
            match ctx with
            | None   -> return None
            | Some c ->
                match c.HttpContext.Response.HasStarted with
                | true  -> return  Some c
                | false -> return! handler c
        }

let (>>=) = bind

The bind function takes in a HttpHandler function and a HttpHandlerResult. It first evaluates the HttpHandlerResult and checks its return value. If there was Some HttpHandlerContext then it will pass it on to the HttpHandler function otherwise it will return None. If the response object inside the HttpHandlerContext has already been written, then it will skip the HttpHandler function as well and return the current HttpHandlerContext as the final result.

The compose combinator combines two HttpHandler functions into one:

let compose (handler : HttpHandler) (handler2 : HttpHandler) =
    fun (ctx : HttpHandlerContext) ->
        handler ctx |> bind handler2

It is probably the more useful combinator as it allows composing many smaller HttpHandler functions into a bigger web application.

If you would like to learn more about the difference between >>= and >=> then please check out Scott Wlaschin's blog post on Railway oriented programming.

The choose combinator function iterates through a list of HttpHandler functions and invokes each individual handler until the first HttpHandler returns a result.

let app = 
    choose [
        route "/foo" >=> text "Foo"
        route "/bar" >=> text "Bar"
    ]

GET, POST, PUT, PATCH, DELETE filters a request by the specified HTTP verb.

let app = 
    choose [
        GET  >=> route "/foo" >=> text "GET Foo"
        POST >=> route "/foo" >=> text "POST Foo"
        route "/bar" >=> text "Always Bar"
    ]

mustAccept filters a request by the Accept HTTP header. You can use it to check if a client accepts a certain mime type before returning a response.

let app = 
    mustAccept [ "text/plain"; "application/json" ] >=>
        choose [
            route "/foo" >=> text "Foo"
            route "/bar" >=> json "Bar"
        ]

challenge challenges an authentication with a specified authentication scheme (authScheme).

let mustBeLoggedIn =
    requiresAuthentication (challenge "Cookie")

let app = 
    choose [
        route "/ping" >=> text "pong"
        route "/admin" >=> mustBeLoggedIn >=> text "You're an admin"
    ]

signOff signs off the currently logged in user.

let app = 
    choose [
        route "/ping" >=> text "pong"
        route "/logout" >=> signOff "Cookie" >=> text "You have successfully logged out."
    ]

requiresAuthentication validates if a user is authenticated/logged in. If the user is not authenticated then the handler will execute the authFailedHandler function.

let mustBeLoggedIn =
    requiresAuthentication (challenge "Cookie")

let app = 
    choose [
        route "/ping" >=> text "pong"
        route "/user" >=> mustBeLoggedIn >=> text "You're a logged in user."
    ]

requiresRole validates if an authenticated user is in a specified role. If the user fails to be in the required role then the handler will execute the authFailedHandler function.

let accessDenied = setStatusCode 401 >=> text "Access Denied"

let mustBeAdmin = 
    requiresAuthentication accessDenied 
    >=> requiresRole "Admin" accessDenied

let app = 
    choose [
        route "/ping" >=> text "pong"
        route "/admin" >=> mustBeAdmin >=> text "You're an admin."
    ]

requiresRoleOf validates if an authenticated user is in one of the supplied roles. If the user fails to be in one of the required roles then the handler will execute the authFailedHandler function.

let accessDenied = setStatusCode 401 >=> text "Access Denied"

let mustBeSomeAdmin = 
    requiresAuthentication accessDenied 
    >=> requiresRoleOf [ "Admin"; "SuperAdmin"; "RootAdmin" ] accessDenied

let app = 
    choose [
        route "/ping" >=> text "pong"
        route "/admin" >=> mustBeSomeAdmin >=> text "You're an admin."
    ]

clearResponse tries to clear the current response. This can be useful inside an error handler to reset the response before writing an error message to the body of the HTTP response object.

let errorHandler (ex : Exception) (ctx : HttpHandlerContext) =
    ctx |> (clearResponse >=> setStatusCode 500 >=> text ex.Message)

let app = 
    choose [
        route "/foo" >=> text "Foo"
        route "/bar" >=> text "Bar"
    ]

type Startup() =
    member __.Configure (app : IApplicationBuilder)
                        (env : IHostingEnvironment)
                        (loggerFactory : ILoggerFactory) =
        app.UseGiraffeErrorHandler(errorHandler)
        app.UseGiraffe(webApp)

route compares a given path with the actual request path and short circuits if it doesn't match.

let app = 
    choose [
        route "/"    >=> text "Index path"
        route "/foo" >=> text "Foo"
        route "/bar" >=> text "Bar"
    ]

routef matches a given format string with the actual request path. On success it will resolve the arguments from the format string and invoke the given HttpHandler with them.

The following format placeholders are currently supported:

• %b for bool
• %c for char
• %s for string
• %i for int32
• %d for int64 (this is custom to Giraffe)
• %f for float/double

let app = 
    choose [
        route  "/foo" >=> text "Foo"
        routef "/bar/%s/%i" (fun (name, age) ->
            // name is of type string
            // age is of type int
            text (sprintf "Name: %s, Age: %i" name age))
    ]

routeCi is the case insensitive version of route.

// "/FoO", "/fOO", "/bAr", etc. will match as well

let app = 
    choose [
        routeCi "/"    >=> text "Index path"
        routeCi "/foo" >=> text "Foo"
        routeCi "/bar" >=> text "Bar"
    ]

routeCif is the case insensitive version of routef.

let app = 
    choose [
        route  "/foo" >=> text "Foo"
        routeCif "/bar/%s/%i" (fun (name, age) ->
            text (sprintf "Name: %s, Age: %i" name age))
    ]

routeStartsWith checks if the current request path starts with the given string. This can be useful when combining with other http handlers, e.g. to validate a subset of routes for authentication.

let app = 
    routeStartsWith "/api/" >=>
        requiresAuthentication (challenge "Cookie") >=>
            choose [
                route "/api/v1/foo" >=> text "Foo"
                route "/api/v1/bar" >=> text "Bar"
            ]

routeStartsWithCi is the case insensitive version of routeStartsWith.

let app = 
    routeStartsWithCi "/api/v1/" >=>
        choose [
            route "/api/v1/foo" >=> text "Foo"
            route "/api/v1/bar" >=> text "Bar"
        ]

subRoute checks if the current path begins with the given path and will invoke the passed in handler if it was a match. The given handler (and any nested handlers within it) should omit the already applied path for subsequent route evaluations.

let app = 
    subRoute "/api"
        (choose [
            subRoute "/v1"
                (choose [
                    route "/foo" >=> text "Foo 1"
                    route "/bar" >=> text "Bar 1" ])
            subRoute "/v2"
                (choose [
                    route "/foo" >=> text "Foo 2"
                    route "/bar" >=> text "Bar 2" ]) ])

subRouteCi is the case insensitive version of subRoute.

let app = 
    subRouteCi "/api"
        (choose [
            subRouteCi "/v1"
                (choose [
                    route "/foo" >=> text "Foo 1"
                    route "/bar" >=> text "Bar 1" ])
            subRouteCi "/v2"
                (choose [
                    route "/foo" >=> text "Foo 2"
                    route "/bar" >=> text "Bar 2" ]) ])

setStatusCode changes the status code of the HttpResponse.

let app = 
    choose [
        route  "/foo" >=> text "Foo"
        setStatusCode 404 >=> text "Not found"
    ]

setHttpHeader sets or modifies a HTTP header of the HttpResponse.

let app = 
    choose [
        route  "/foo" >=> text "Foo"
        setStatusCode 404 >=> setHttpHeader "X-CustomHeader" "something" >=> text "Not found"
    ]

setBody sets or modifies the body of the HttpResponse. This http handler triggers a response to the client and other http handlers will not be able to modify the HTTP headers afterwards any more.

let app = 
    choose [
        route  "/foo" >=> setBody (Encoding.UTF8.GetBytes "Some string")
    ]

setBodyAsString sets or modifies the body of the HttpResponse. This http handler triggers a response to the client and other http handlers will not be able to modify the HTTP headers afterwards any more.

let app = 
    choose [
        route  "/foo" >=> setBodyAsString "Some string"
    ]

text sets or modifies the body of the HttpResponse by sending a plain text value to the client.. This http handler triggers a response to the client and other http handlers will not be able to modify the HTTP headers afterwards any more.

The different between text and setBodyAsString is that this http handler also sets the Content-Type HTTP header to text/plain.

let app = 
    choose [
        route  "/foo" >=> text "Some string"
    ]

json sets or modifies the body of the HttpResponse by sending a JSON serialized object to the client. This http handler triggers a response to the client and other http handlers will not be able to modify the HTTP headers afterwards any more. It also sets the Content-Type HTTP header to application/json.

type Person =
    {
        FirstName : string
        LastName  : string
    }

let app = 
    choose [
        route  "/foo" >=> json { FirstName = "Foo"; LastName = "Bar" }
    ]

xml sets or modifies the body of the HttpResponse by sending an XML serialized object to the client. This http handler triggers a response to the client and other http handlers will not be able to modify the HTTP headers afterwards any more. It also sets the Content-Type HTTP header to application/xml.

[<CLIMutable>]
type Person =
    {
        FirstName : string
        LastName  : string
    }

let app = 
    choose [
        route  "/foo" >=> xml { FirstName = "Foo"; LastName = "Bar" }
    ]

negotiate sets or modifies the body of the HttpResponse by inspecting the Accept header of the HTTP request and deciding if the response should be sent in JSON or XML. If the client is indifferent then the default response will be sent in JSON.

This http handler triggers a response to the client and other http handlers will not be able to modify the HTTP headers afterwards any more.

[<CLIMutable>]
type Person =
    {
        FirstName : string
        LastName  : string
    }

let app = 
    choose [
        route  "/foo" >=> negotiate { FirstName = "Foo"; LastName = "Bar" }
    ]

negotiateWith sets or modifies the body of the HttpResponse by inspecting the Accept header of the HTTP request and deciding in what mimeType the response should be sent. A dictionary of type IDictionary<string, obj -> HttpHandler> is used to determine which obj -> HttpHandler function should be used to convert an object into a HttpHandler for a given mime type.

This http handler triggers a response to the client and other http handlers will not be able to modify the HTTP headers afterwards any more.

[<CLIMutable>]
type Person =
    {
        FirstName : string
        LastName  : string
    }

// xml and json are the two HttpHandler functions from above
let rules =
    dict [
        "*/*"             , xml
        "application/json", json
        "application/xml" , xml
    ]

let app = 
    choose [
        route  "/foo" >=> negotiateWith rules { FirstName = "Foo"; LastName = "Bar" }
    ]

htmlFile sets or modifies the body of the HttpResponse with the contents of a physical html file. This http handler triggers a response to the client and other http handlers will not be able to modify the HTTP headers afterwards any more.

This http handler takes a relative path of a html file as input parameter and sets the HTTP header Content-Type to text/html.

let app = 
    choose [
        route  "/" >=> htmlFile "index.html"
    ]

dotLiquid uses the DotLiquid template engine to set or modify the body of the HttpResponse. This http handler triggers a response to the client and other http handlers will not be able to modify the HTTP headers afterwards any more.

The dotLiquid handler requires the content type and the actual template to be passed in as two string values together with an object model. This handler is supposed to be used as the base handler for other http handlers which want to utilize the DotLiquid template engine (e.g. you could create an SVG handler on top of it).

type Person =
    {
        FirstName : string
        LastName  : string
    }

let template = "<html><head><title>DotLiquid</title></head><body><p>First name: {{ firstName }}<br />Last name: {{ lastName }}</p></body></html>

let app = 
    choose [
        route  "/foo" >=> dotLiquid "text/html" template { FirstName = "Foo"; LastName = "Bar" }
    ]

dotLiquidTemplate uses the DotLiquid template engine to set or modify the body of the HttpResponse. This http handler triggers a response to the client and other http handlers will not be able to modify the HTTP headers afterwards any more.

This http handler takes a relative path of a template file, an associated model and the contentType of the response as parameters.

type Person =
    {
        FirstName : string
        LastName  : string
    }

let app = 
    choose [
        route  "/foo" >=> dotLiquidTemplate "text/html" "templates/person.html" { FirstName = "Foo"; LastName = "Bar" }
    ]

dotLiquidHtmlView is the same as dotLiquidTemplate except that it automatically sets the response as text/html.

type Person =
    {
        FirstName : string
        LastName  : string
    }

let app = 
    choose [
        route  "/foo" >=> dotLiquidHtmlView "templates/person.html" { FirstName = "Foo"; LastName = "Bar" }
    ]

razorView uses the official ASP.NET Core MVC Razor view engine to compile a page and set the body of the HttpResponse. This http handler triggers a response to the client and other http handlers will not be able to modify the HTTP headers afterwards any more.

The razorView handler requires the view name, an object model and the contentType of the response to be passed in. It also requires to be enabled through the AddRazorEngine function during start-up.

Add the razor engine service during start-up:

type Startup() =
    member __.ConfigureServices (services : IServiceCollection, env : IHostingEnvironment) =    
        let viewsFolderPath = Path.Combine(env.ContentRootPath, "views")
        services.AddRazorEngine(viewsFolderPath) |> ignore

Use the razorView function:

let model = { WelcomeText = "Hello World" }

let app = 
    choose [
        // Assuming there is a view called "Index.cshtml"
        route  "/" >=> razorView "text/html" "Index" model
    ]

razorHtmlView is the same as razorView except that it automatically sets the response as text/html.

Add the razor engine service during start-up:

type Startup() =
    member __.ConfigureServices (services : IServiceCollection, env : IHostingEnvironment) =    
        let viewsFolderPath = Path.Combine(env.ContentRootPath, "views")
        services.AddRazorEngine(viewsFolderPath) |> ignore

Use the razorView function:

let model = { WelcomeText = "Hello World" }

let app = 
    choose [
        // Assuming there is a view called "Index.cshtml"
        route  "/" >=> razorHtmlView "Index" model
    ]

renderHtml is a more functional way of generating HTML by composing HTML elements in F# to generate a rich Model-View output.

It is based on Suave's Experimental Html and bears some resemblance with Elm.

Create a function that accepts a model and returns a HtmlNode:

open Giraffe.HtmlEngine

let model = { Name = "John Doe" }

let layout (content: HtmlNode list) =
    html [] [
        head [] [
            title [] (encodedText "Giraffe")
        ]
        body [] content
    ]

let partial () =
    p [] (encodedText "Some partial text.")

let personView model =
    [
        div [] [
                h3 [] (sprintf "Hello, %s" model.Name |> encodedText)
            ]
        div [] [partial()]
    ] |> layout

let app = 
    choose [
        route "/" >=> (personView model |> renderHtml)
    ]

If your route is not returning a static response, then you should wrap your function with a warbler.

// unit -> string
let time() =
    System.DateTime.Now.ToString()

let webApp = 
    choose [
        GET >=>
            choose [
                route "/once"      >=> (time() |> text)
                route "/everytime" >=> warbler (fun _ -> (time() |> text))
            ]
    ]

Functions in F# are eagerly evaluated and the /once route will only be evaluated the first time. A warbler will help to evaluate the function every time the route is hit.

// ('a -> 'a -> 'b) -> 'a -> 'b
let warbler f a = f a a

Defining a new HttpHandler is fairly easy. All you need to do is to create a new function which matches the signature of HttpHandlerContext -> Async<HttpHandlerContext option>. Through currying your custom HttpHandler can extend the original signature as long as the partial application of your function will still return a function of HttpHandlerContext -> Async<HttpHandlerContext option>.

Defining a custom HTTP handler to partially filter a route:

(After creating this example I added the routeStartsWith HttpHandler to the list of default handlers as it turned out to be quite useful)

let routeStartsWith (subPath : string) =
    fun ctx ->
        if ctx.HttpContext.Request.Path.ToString().StartsWith subPath 
        then Some ctx
        else None
        |> async.Return

Defining another custom HTTP handler to validate a mandatory HTTP header:

let requiresToken (expectedToken : string) (handler : HttpHandler) =
    fun ctx ->
        let token    = ctx.HttpContext.Request.Headers.["X-Token"].ToString()
        let response =
            if token.Equals(expectedToken)
            then handler
            else setStatusCode 401 >=> text "Token wrong or missing"
        response ctx

Composing a web application from smaller HTTP handlers:

let app = 
    choose [
        route "/"       >=> htmlFile "index.html"
        route "/about"  >=> htmlFile "about.html"
        routeStartsWith "/api/v1/" >=>
            requiresToken "secretToken" (
                choose [
                    route "/api/v1/foo" >=> text "something"
                    route "/api/v1/bar" >=> text "bar"
                ]
            )
        setStatusCode 404 >=> text "Not found"
    ] : HttpHandler

The Giraffe.ModelBinding module exposes a default set of model binding functions which can be used from within a HttpHandler.

bindJson<'T> (ctx : HttpHandlerContext) can be used to bind a JSON payload to a strongly typed model.

Define an F# record type with the CLIMutable attribute which will add a parameterless constructor to the type:

[<CLIMutable>]
type Car =
    {
        Name   : string
        Make   : string
        Wheels : int
        Built  : DateTime
    }

Then create a new HttpHandler which uses bindJson and use it from an app:

open Giraffe.HttpHandlers
open Giraffe.ModelBinding

let submitCar =
    fun ctx ->
        async {
            // Binds a JSON payload to a Car object
            let! car = bindJson<Car> ctx

            // Serializes the Car object back into JSON
            // and sends it back as the response.
            return! json car ctx
        }

let webApp =
    choose [
        GET >=>
            choose [
                route "/"    >=> text "index"
                route "ping" >=> text "pong" ]
        POST >=> route "/car" >=> submitCar ]

You can test the bind function by sending a HTTP request with a JSON payload:

POST http://localhost:5000/car HTTP/1.1
Host: localhost:5000
Connection: keep-alive
Content-Length: 77
Cache-Control: no-cache
Content-Type: application/json
Accept: */*

{ "Name": "DB9", "Make": "Aston Martin", "Wheels": 4, "Built": "2016-01-01" }

bindXml<'T> (ctx : HttpHandlerContext) can be used to bind an XML payload to a strongly typed model.

Define an F# record type with the CLIMutable attribute which will add a parameterless constructor to the type:

[<CLIMutable>]
type Car =
    {
        Name   : string
        Make   : string
        Wheels : int
        Built  : DateTime
    }

Then create a new HttpHandler which uses bindXml and use it from an app:

open Giraffe.HttpHandlers
open Giraffe.ModelBinding

let submitCar =
    fun ctx ->
        async {
            // Binds an XML payload to a Car object
            let! car = bindXml<Car> ctx

            // Serializes the Car object back into JSON
            // and sends it back as the response.
            return! json car ctx
        }

let webApp =
    choose [
        GET >=>
            choose [
                route "/"    >=> text "index"
                route "ping" >=> text "pong" ]
        POST >=> route "/car" >=> submitCar ]

You can test the bind function by sending a HTTP request with an XML payload:

POST http://localhost:5000/car HTTP/1.1
Host: localhost:5000
Connection: keep-alive
Content-Length: 104
Cache-Control: no-cache
Content-Type: application/xml
Accept: */*

<Car>
    <Name>DB9</Name>
    <Make>Aston Martin</Make>
    <Wheels>4</Wheels>
    <Built>2016-01-01</Built>
</Car>

bindForm<'T> (ctx : HttpHandlerContext) can be used to bind a form urlencoded payload to a strongly typed model.

Define an F# record type with the CLIMutable attribute which will add a parameterless constructor to the type:

[<CLIMutable>]
type Car =
    {
        Name   : string
        Make   : string
        Wheels : int
        Built  : DateTime
    }

Then create a new HttpHandler which uses bindForm and use it from an app:

open Giraffe.HttpHandlers
open Giraffe.ModelBinding

let submitCar =
    fun ctx ->
        async {
            // Binds a form urlencoded payload to a Car object
            let! car = bindForm<Car> ctx

            // Serializes the Car object back into JSON
            // and sends it back as the response.
            return! json car ctx
        }

let webApp =
    choose [
        GET >=>
            choose [
                route "/"    >=> text "index"
                route "ping" >=> text "pong" ]
        POST >=> route "/car" >=> submitCar ]

You can test the bind function by sending a HTTP request with a form payload:

POST http://localhost:5000/car HTTP/1.1
Host: localhost:5000
Connection: keep-alive
Content-Length: 52
Cache-Control: no-cache
Content-Type: application/x-www-form-urlencoded
Accept: */*

Name=DB9&Make=Aston+Martin&Wheels=4&Built=2016-01-01

bindQueryString<'T> (ctx : HttpHandlerContext) can be used to bind a query string to a strongly typed model.

Define an F# record type with the CLIMutable attribute which will add a parameterless constructor to the type:

[<CLIMutable>]
type Car =
    {
        Name   : string
        Make   : string
        Wheels : int
        Built  : DateTime
    }

Then create a new HttpHandler which uses bindQueryString and use it from an app:

open Giraffe.HttpHandlers
open Giraffe.ModelBinding

let submitCar =
    fun ctx ->
        async {
            // Binds a query string to a Car object
            let! car = bindQueryString<Car> ctx

            // Serializes the Car object back into JSON
            // and sends it back as the response.
            return! json car ctx
        }

let webApp =
    choose [
        GET >=>
            choose [
                route "/"    >=> text "index"
                route "ping" >=> text "pong"
                route "/car" >=> submitCar ]

You can test the bind function by sending a HTTP request with a query string:

GET http://localhost:5000/car?Name=Aston%20Martin&Make=DB9&Wheels=4&Built=1990-04-20 HTTP/1.1
Host: localhost:5000
Cache-Control: no-cache
Accept: */*

bindModel<'T> (ctx : HttpHandlerContext) can be used to automatically detect the method and Content-Type of a HTTP request and automatically bind a JSON, XML,or form urlencoded payload or a query string to a strongly typed model.

Define an F# record type with the CLIMutable attribute which will add a parameterless constructor to the type:

[<CLIMutable>]
type Car =
    {
        Name   : string
        Make   : string
        Wheels : int
        Built  : DateTime
    }

Then create a new HttpHandler which uses bindModel and use it from an app:

open Giraffe.HttpHandlers
open Giraffe.ModelBinding

let submitCar =
    fun ctx ->
        async {
            // Binds a JSON, XML or form urlencoded payload to a Car object
            let! car = bindModel<Car> ctx

            // Serializes the Car object back into JSON
            // and sends it back as the response.
            return! json car ctx
        }

let webApp =
    choose [
        GET >=>
            choose [
                route "/"    >=> text "index"
                route "ping" >=> text "pong" ]
        // Can accept GET and POST requests and
        // bind a model from the payload or query string
        route "/car" >=> submitCar ]

The easiest way to get started with Giraffe is by installing the giraffe-template NuGet package, which adds a new template to your dotnet new command:

dotnet new -i giraffe-template::*

Afterwards you can create a new Giraffe application by running dotnet new giraffe.

Install the Giraffe NuGet package:

PM> Install-Package Giraffe

Create a web application and plug it into the ASP.NET Core middleware:

open Giraffe.HttpHandlers
open Giraffe.Middleware

let webApp = 
    choose [
        route "/ping"   >=> text "pong"
        route "/"       >=> htmlFile "/pages/index.html" ]

type Startup() =
    member __.Configure (app : IApplicationBuilder)
                        (env : IHostingEnvironment)
                        (loggerFactory : ILoggerFactory) =
        
        app.UseGiraffe(webApp)

There is a basic sample application in the /samples/SampleApp folder.

More sample applications will be added in the future.

Currently Giraffe has only been tested against a simple plain text route and measured the total amount of handled requests per second. The latest result yielded an average of 79093 req/s over a period of 10 seconds, which was only closely after plain Kestrel which was capable of handling 79399 req/s on average.

Please check out Jimmy Byrd's dotnet-web-benchmarks for more details.

Giraffe is built with the latest .NET Core SDK.

You can either install Visual Studio 2017 which comes with the latest SDK or manually download and install the .NET SDK 1.1.

After installation you should be able to run build.cmd to successfully build, test and package the library.

Currently the best way to work with F# on .NET Core is to use Visual Studio Code with the Ionide extension. Intellisense and debugging is supported with the latest versions of both.

Help and feedback is always welcome and pull requests get accepted.

When contributing to this repository, please first discuss the change you wish to make via an open issue before submitting a pull request. For new feature requests please describe your idea in more detail and how it could benefit other users as well.

Please be aware that Giraffe strictly aims to remain as light as possible while providing generic functionality for building functional web applications. New feature work must be applicable to a broader user base and if this requirement cannot be met sufficiently then a pull request might get rejected. In the case of doubt the maintainer will rather reject a potentially useful feature than adding one too many. This measure is to protect the repository from feature bloat over time and shall not be taken personally.

When making changes please use existing code as a guideline for coding style and documentation. If you intend to add or change an existing HttpHandler then please update the README.md file to reflect these changes there as well. If applicable unit tests must be be added or updated and the project must successfully build before a pull request can be accepted.

If you have any further questions please let me know.

You can file an issue on GitHub or contact me via https://dusted.codes/about.

Special thanks to all developers who helped me by submitting pull requests with new feature work, bug fixes and other improvements to keep the project in good shape (in no particular order):

• slang25 (Added subRoute feature and general help to keep things in good shape)
• Nicolás Herrera (Added razor engine feature)
• Dave Shaw (Extended sample application and general help to keep things in good shape)
• Tobias Burger (Fixed issues with culture specific parsers)
• David Sinclair (Created the dotnet-new template for Giraffe)
• Florian Verdonck (Ported Suave's experimental Html into Giraffe, implemented the warbler and general help with the project)

If you submit a pull request please feel free to add yourself to this list as part of the PR.

Apache 2.0