wpf - 将 WPF 的控件绑定(bind)到 F# 选项

Question

假设我有一个业务对象(没有 AllowNullLiteralAttribute )。

type Person(name: string) =
    member val Name = name
    override x.ToString() = name

还有一个 View 模型，可选择设置所选人员。

type MainWindowModel() =

    let mutable selectedPerson: Person option = None
        :
    member val People = ObservableCollection<Person>()
    member x.SelectedPerson
        with get() = selectedPerson
        and set(v) =
            if selectedPerson <> v then
                selectedPerson <- v
                x.RaisePropertyChanged("SelectedPerson")

绑定(bind) WPF 控件的 SelectedItem 的最佳方法是什么？属性到 F# 选项属性(不使用 AllowNullLiteralAttribute )？

如果我这样做...

<StackPanel>
    <ListBox ItemsSource="{Binding People}"
             SelectedItem="{Binding SelectedPerson}"
             DisplayMemberPath="Name" />
    <TextBlock Text="{Binding SelectedPerson}" />
</StackPanel>

...导致错误，无法将“George”从“Person”类型转换为“Microsoft.FSharp.Core.FSharpOption`1[Person]”类型

Answer 1

我目前采取的方法是自己写IValueConverter .

open System
open System.Globalization
open System.Windows.Data

type OptionsTypeConverter() =

    // from http://stackoverflow.com/questions/6289761
    let (|SomeObj|_|) =
      let ty = typedefof<option<_>>
      fun (a:obj) ->
        let aty = a.GetType()
        let v = aty.GetProperty("Value")
        if aty.IsGenericType && aty.GetGenericTypeDefinition() = ty then
          if a = null then None
          else Some(v.GetValue(a, [| |]))
        else None

    interface IValueConverter with

        member x.Convert(value: obj, targetType: Type, parameter: obj, culture: CultureInfo) =
            match value with
            | null -> null
            | SomeObj(v) -> v
            | _ -> value

        member x.ConvertBack(value: obj, targetType: Type, parameter: obj, culture: CultureInfo) =
            match value with
            | null -> None :> obj
            | x -> Activator.CreateInstance(targetType, [| x |])

然后我的 XAML 看起来像这样:

<StackPanel>
    <ListBox ItemsSource="{Binding People}"
             SelectedItem="{Binding SelectedPerson, Converter={StaticResource OptionsTypeConverter1}}"
             DisplayMemberPath="Name" />
    <TextBlock Text="{Binding SelectedPerson, Converter={StaticResource OptionsTypeConverter1}}" />
</StackPanel>

可能有更简单的方法。该转换器可能已经存在于框架中。那里可能有更好的实现。