Twenty six low-risk ways to use F# at work

let x = 1
let y = 2
x + y;;

open System
DateTime.Now.ToString("yyyy-MM-dd hh:mm")  // "2014-04-18 01:08"
DateTime.Now.ToString("yyyy-MM-dd HH:mm")  // "2014-04-18 13:09"

// TIP: sets the current directory to be same as the script directory
System.IO.Directory.SetCurrentDirectory (__SOURCE_DIRECTORY__)

open System

[<CLIMutable>]
type DateSerTest = {Local:DateTime;Utc:DateTime}

let ser = new System.Xml.Serialization.XmlSerializer(typeof<DateSerTest>)

let testSerialization (dt:DateSerTest) =
    let filename = "serialization.xml"
    use fs = new IO.FileStream(filename , IO.FileMode.Create)
    ser.Serialize(fs, o=dt)
    fs.Close()
    IO.File.ReadAllText(filename) |> printfn "%s"

let d = {
    Local = DateTime.SpecifyKind(new DateTime(2014,7,4), DateTimeKind.Local)
    Utc = DateTime.SpecifyKind(new DateTime(2014,7,4), DateTimeKind.Utc)
    }

testSerialization d

<DateSerTest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Local>2014-07-04T00:00:00+01:00</Local>
  <Utc>2014-07-04T00:00:00Z</Utc>
</DateSerTest>

Environment.GetEnvironmentVariable "ProgramFiles" =
    Environment.GetEnvironmentVariable "PROGRAMFILES"
// answer => true

// set the current directory to be same as the script directory
System.IO.Directory.SetCurrentDirectory (__SOURCE_DIRECTORY__)

// pass in the relative path to the DLL
#r @"bin\debug\myapp.dll"

// open the namespace
open MyApp

// do something
MyApp.DoSomething()

// sets the current directory to be same as the script directory
System.IO.Directory.SetCurrentDirectory (__SOURCE_DIRECTORY__)

// assumes nuget install Microsoft.AspNet.WebApi.OwinSelfHost has been run
// so that assemblies are available under the current directory
#r @"Packages\Owin\lib\net40\Owin.dll"
#r @"Packages\Microsoft.Owin\lib\net40\Microsoft.Owin.dll"
#r @"Packages\Microsoft.Owin.Host.HttpListener\lib\net40\Microsoft.Owin.Host.HttpListener.dll"
#r @"Packages\Microsoft.Owin.Hosting\lib\net40\Microsoft.Owin.Hosting.dll"
#r @"Packages\Microsoft.AspNet.WebApi.Owin\lib\net45\System.Web.Http.Owin.dll"
#r @"Packages\Microsoft.AspNet.WebApi.Core\lib\net45\System.Web.Http.dll"
#r @"Packages\Microsoft.AspNet.WebApi.Client\lib\net45\System.Net.Http.Formatting.dll"
#r @"Packages\Newtonsoft.Json\lib\net40\Newtonsoft.Json.dll"
#r "System.Net.Http.dll"

open System
open Owin
open Microsoft.Owin
open System.Web.Http
open System.Web.Http.Dispatcher
open System.Net.Http.Formatting

module OwinSelfhostSample =

    /// a record to return
    [<CLIMutable>]
    type Greeting = { Text : string }

    /// A simple Controller
    type GreetingController() =
        inherit ApiController()

        // GET api/greeting
        member this.Get()  =
            {Text="Hello!"}

    /// Another Controller that parses URIs
    type ValuesController() =
        inherit ApiController()

        // GET api/values
        member this.Get()  =
            ["value1";"value2"]

        // GET api/values/5
        member this.Get id =
            sprintf "id is %i" id

        // POST api/values
        member this.Post ([<FromBody>]value:string) =
            ()

        // PUT api/values/5
        member this.Put(id:int, [<FromBody>]value:string) =
            ()

        // DELETE api/values/5
        member this.Delete(id:int) =
            ()

    /// A helper class to store routes, etc.
    type ApiRoute = { id : RouteParameter }

    /// IMPORTANT: When running interactively, the controllers will not be found with error:
    /// "No type was found that matches the controller named 'XXX'."
    /// The fix is to override the ControllerResolver to use the current assembly
    type ControllerResolver() =
        inherit DefaultHttpControllerTypeResolver()

        override this.GetControllerTypes (assembliesResolver:IAssembliesResolver) =
            let t = typeof<System.Web.Http.Controllers.IHttpController>
            System.Reflection.Assembly.GetExecutingAssembly().GetTypes()
            |> Array.filter t.IsAssignableFrom
            :> Collections.Generic.ICollection<Type>

    /// A class to manage the configuration
    type MyHttpConfiguration() as this =
        inherit HttpConfiguration()

        let configureRoutes() =
            this.Routes.MapHttpRoute(
                name= "DefaultApi",
                routeTemplate= "api/{controller}/{id}",
                defaults= { id = RouteParameter.Optional }
                ) |> ignore

        let configureJsonSerialization() =
            let jsonSettings = this.Formatters.JsonFormatter.SerializerSettings
            jsonSettings.Formatting <- Newtonsoft.Json.Formatting.Indented
            jsonSettings.ContractResolver <-
                Newtonsoft.Json.Serialization.CamelCasePropertyNamesContractResolver()

        // Here is where the controllers are resolved
        let configureServices() =
            this.Services.Replace(
                typeof<IHttpControllerTypeResolver>,
                new ControllerResolver())

        do configureRoutes()
        do configureJsonSerialization()
        do configureServices()

    /// Create a startup class using the configuration
    type Startup() =

        // This code configures Web API. The Startup class is specified as a type
        // parameter in the WebApp.Start method.
        member this.Configuration (appBuilder:IAppBuilder) =
            // Configure Web API for self-host.
            let config = new MyHttpConfiguration()
            appBuilder.UseWebApi(config) |> ignore


// Start OWIN host
do
    // Create server
    let baseAddress = "http://localhost:9000/"
    use app = Microsoft.Owin.Hosting.WebApp.Start<OwinSelfhostSample.Startup>(url=baseAddress)

    // Create client and make some requests to the api
    use client = new System.Net.Http.HttpClient()

    let showResponse query =
        let response = client.GetAsync(baseAddress + query).Result
        Console.WriteLine(response)
        Console.WriteLine(response.Content.ReadAsStringAsync().Result)

    showResponse "api/greeting"
    showResponse "api/values"
    showResponse "api/values/42"

    // for standalone scripts, pause so that you can test via your browser as well
    Console.ReadLine() |> ignore

StatusCode: 200, ReasonPhrase: 'OK', Version: 1.1, Content: System.Net.Http.StreamContent, Headers:
{
  Date: Fri, 18 Apr 2014 22:29:04 GMT
  Server: Microsoft-HTTPAPI/2.0
  Content-Length: 24
  Content-Type: application/json; charset=utf-8
}
{
  "text": "Hello!"
}
StatusCode: 200, ReasonPhrase: 'OK', Version: 1.1, Content: System.Net.Http.StreamContent, Headers:
{
  Date: Fri, 18 Apr 2014 22:29:04 GMT
  Server: Microsoft-HTTPAPI/2.0
  Content-Length: 29
  Content-Type: application/json; charset=utf-8
}
[
  "value1",
  "value2"
]
StatusCode: 200, ReasonPhrase: 'OK', Version: 1.1, Content: System.Net.Http.StreamContent, Headers:
{
  Date: Fri, 18 Apr 2014 22:29:04 GMT
  Server: Microsoft-HTTPAPI/2.0
  Content-Length: 10
  Content-Type: application/json; charset=utf-8
}
"id is 42"

open System.Windows.Forms
open System.Drawing

let form = new Form(Width= 400, Height = 300, Visible = true, Text = "Hello World")
form.TopMost <- true
form.Click.Add (fun _ ->
    form.Text <- sprintf "form clicked at %i" DateTime.Now.Ticks)
form.Show()

let panel = new FlowLayoutPanel()
form.Controls.Add(panel)
panel.Dock = DockStyle.Fill
panel.WrapContents <- false

let greenButton = new Button()
greenButton.Text <- "Make the background color green"
greenButton.Click.Add (fun _-> form.BackColor <- Color.LightGreen)
panel.Controls.Add(greenButton)

greenButton.AutoSize <- true

let yellowButton = new Button()
yellowButton.Text <- "Make me yellow"
yellowButton.AutoSize <- true
yellowButton.Click.Add (fun _-> form.BackColor <- Color.Yellow)
panel.Controls.Add(yellowButton)

panel.FlowDirection <- FlowDirection.TopDown

yellowButton.Dock <- DockStyle.Fill