DialogResult in F#

Question

在试图从MVVM应用程序的窗口中检索DialogResult时，我偶然发现了this previous question。在实现建议的更改之后，示例如下所示：

type DialogCloser() =

    static let DialogResultProperty =
        DependencyProperty.RegisterAttached("DialogResult", typeof<bool>, typeof<DialogCloser>, new PropertyMetadata(DialogResultChanged))

    static member GetDialogResult (a:DependencyObject) =
        a.GetValue(DialogResultProperty) :?> bool

    static member SetDialogResult (a:DependencyObject) (value:string) = 
        a.SetValue(DialogResultProperty, value)

    member this.DialogResultChanged (a:DependencyObject) (e:DependencyPropertyChangedEventArgs) =
        let window = a :?> Window
        match window with
        | null -> failwith "Not a Window"
        | _ -> window.DialogResult <- System.Nullable (e.NewValue :?> bool)

现在在声明DialogResultChanged之前使用它，当然这在F#中不计算。

我似乎找不到一个可行的解决办法，任何帮助都将不胜感激。

Answer 1

我不是WPF专家，但在this related C# solution中，DialogResultsChanged方法是静态的。如果在F#中也将该方法定义为静态方法，则应该能够在声明它之前引用它(使用全名DialogCloser.DialogResultsChanged)，所以如下所示应该可以做到这一点：

type DialogCloser() =

    static let DialogResultProperty =
        DependencyProperty.RegisterAttached
            ( "DialogResult", typeof<bool>, typeof<DialogCloser>, 
              new PropertyMetadata(DialogCloser.DialogResultChanged))

    static member GetDialogResult (a:DependencyObject) =
        a.GetValue(DialogResultProperty) :?> bool

    static member SetDialogResult (a:DependencyObject) (value:string) = 
        a.SetValue(DialogResultProperty, value)

    static member DialogResultChanged 
            (a:DependencyObject) (e:DependencyPropertyChangedEventArgs) =
        let window = a :?> Window
        match window with
        | null -> failwith "Not a Window"
        | _ -> window.DialogResult <- System.Nullable (e.NewValue :?> bool)