Program.fs

module ConsoleApp.Wpf.Program
open System
open Elmish
open Elmish.WPF
open FSharp.Control.Reactive
       
type Model =
    {   Contacts: Rolodex.Contact seq
        ContactsFilter: string
        ContactsFilterChanged: System.Reactive.Subjects.Subject<string> }

type Msg =
    | SetContactsFilter of string
    | WaitForRx
    
/// Wraps the Rolodex MVU bits in a class with an injectable facade.
type RolodexMVU(facade: Rolodex.Facade) =
    let contacts = facade.GetContacts()

    let init () =
        {   Contacts = []
            ContactsFilter = ""
            ContactsFilterChanged = Subject<string>.broadcast }

    let update msg m =
        match msg with
        | SetContactsFilter filterText -> 
            { m with Contacts = contacts |> Seq.filter (fun c -> c.Name.ToLower().Contains(filterText.ToLower())) }
        | WaitForRx -> m
                
    let bindings model dispatch =
        [
            "Contacts" |> Binding.oneWay (fun m -> m.Contacts)
            "ContactsFilter" |> Binding.twoWay
                (fun m -> m.ContactsFilter)
                (fun v m -> 
                    m.ContactsFilterChanged.OnNext(v)
                    WaitForRx
                )
        ]
 
    let rxSubcription model =
        Cmd.ofSub (fun dispatch -> 
        
            // Subscribe to observable
            model.ContactsFilterChanged
            |> Observable.throttle (TimeSpan.FromMilliseconds(500.0))
            |> Observable.distinctUntilChanged
            |> Observable.subscribe (fun filterText ->
                filterText |> SetContactsFilter |> dispatch
            ) 
            |> ignore

            model.ContactsFilterChanged 
            |> Subject.onNext "" // "Prime the Pump"
            |> ignore
        )

    member this.ShowView() =
        Program.mkSimple init update bindings
        |> Program.withSubscription rxSubcription
        |> Program.withConsoleTrace
        |> Program.runWindowWithConfig
            { ElmConfig.Default with LogConsole = true }
            (Views.RolodexView())


[<EntryPoint; STAThread>]
let main argv =
    let mvu = new RolodexMVU(new Rolodex.Facade())
    mvu.ShowView()

RolodexView.xaml

<Window x:Class="ConsoleApp.Wpf.Views.RolodexView"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:ConsoleApp.Wpf.Views"
        mc:Ignorable="d"
        Title="Contacts" Height="450" Width="400">
    <DockPanel LastChildFill="True" Margin="5" >
        <Grid DockPanel.Dock="Top">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="50" />
                <ColumnDefinition Width="*" />
            </Grid.ColumnDefinitions>
            <Label>Filter:</Label>
            <TextBox Grid.Column="1" Text="{Binding ContactsFilter, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Width="Auto"></TextBox>
        </Grid>
        <ListBox DockPanel.Dock="Bottom" ItemsSource="{Binding Contacts}">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}" />
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </DockPanel>
</Window>