How do I enable CORS in Giraffe? - asp.net-web-api

Question

I am unable to successfully perform a Post operation using the Giraffe framework on the server with an Elm client sending the request.
I receive the following message when attempting to test an http request:
info: Microsoft.AspNetCore.Hosting.Internal.WebHost1
Request starting HTTP/1.1 OPTIONS http://localhost:5000/register 0
Microsoft.AspNetCore.Hosting.Internal.WebHost:Information: Request
starting HTTP/1.1 OPTIONS http://localhost:5000/register 0 dbug:
Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware1
OPTIONS requests are not supported
The service implementation is the following:
let private registrationHandler =
fun(context: HttpContext) ->
async {
let! data = context.BindJson<RegistrationRequest>()
match register data with
| Success profile -> return! json profile context
| Failure -> return! (setStatusCode 400 >=> json "registration failed") context
}
I then attempted the following and observed the same result:
let private registrationHandler =
fun(context: HttpContext) ->
async {
return! text "hello world" context
}
Appendix:
POST >=>
choose [
route "/register" >=> registrationHandler
]
The source file can be found here.
Elm and CORS
WebAPI enable Cors
Here's a Giraffe sample that shows the code for supporting Cors.

Answer 1

Add package: Microsoft.AspNetCore.Cors
In .fs file add:
open Microsoft.AspNetCore.Cors
Add UseCors e.g.:
let configureApp (app : IApplicationBuilder) =
app.UseGiraffeErrorHandler errorHandler
app.UseStaticFiles() |> ignore
app.UseAuthentication() |> ignore
app.UseCors(Action<_>(fun (b: Infrastructure.CorsPolicyBuilder) -> b.AllowAnyHeader() |> ignore; b.AllowAnyMethod() |> ignore)) |> ignore
app.UseGiraffe webApp
In services add cors:
let configureServices (services : IServiceCollection) =
let sp = services.BuildServiceProvider()
let env = sp.GetService<IHostingEnvironment>()
let viewsFolderPath = Path.Combine(env.ContentRootPath, "Views")
services
.AddCors()
.AddAuthentication(authScheme)
.AddCookie(cookieAuth)
|> ignore