将方法绑定到委托类型 DependencyProperty

Question

在 myUserControl.xaml.cs 我有一个名为“IsExtensionValid”的 bool DependencyProperty，其值由以下几行分配：

    bool a = TargetFile.Extension.MatchFileMask(FileFilters, true);
    bool b = (FileValidator is null) ? true : FileValidator(TargetFile).Item1;
    IsExtensionValid = (a && b);

其中FileFilters 和FileValidator 分别是字符串和委托类型DependencyProperty，FileValidator 的委托类型定义为：

    public delegate Tuple<bool, string> ExtraValidation(FileInfo fileInfo);
    public delegate Tuple<bool, string> StaticExtraValidation(FileInfo fileInfo, object o);
    // I also tried this static version with corresponding modifications to the function definition and usages (see below) but still couldn't bind

在mainwindow.xaml.cs中，我定义了一个函数：

    public Tuple<bool, string> ValidateMinFile(FileInfo f) // ExtraValidation delegate
    { return new Tuple<bool, string>(true, "File is invalid"); }
    // meaningful test logic removed but principle stands

在 mainwindow.xaml 我正在尝试通过 xaml 绑定 myUserControlInstance.FileValidator = ValidateMinFile。我尝试了多种方法组合，包括是否使ValidateMinFile 静态、是否作为资源包含、是否作为RelativeSource 引用，以及更多我不记得的方法。我当前的迭代（翻译为人为的示例土地）是：

<local:myUserControl x:Name="MinFileControl"
                       FileFilters="Min Files|*.min"
                       FileValidator="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:}}, Path=ValidateMinFile}"/>

真正的线条实际上是这样的：

<local:FileSelectGroup x:Name="fsgMinFile" DockPanel.Dock="Top" Margin="2"
                       Title="Min file:"
                       FileFilters="Min Files|*.min"
                       PropertyChanged="fsgMinFile_PropertyChanged"
                       FileValidator="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:mainwindow}}, Path=ValidateMinFile}"/>

编辑：我尝试的另一件事是创建一个委托类型作为主窗口的属性并将其设置为引用ValidateMinFile的静态版本

FileSelectGroup.ExtraValidation ValidateMinFileDelegate = ValidateMinFile;`

使用 ValidateMinFile 静态，但是当我在 myUserControl 中访问 FileValidator 的行（带有 bool b = FileValidator... 的行）处断点时，FileValidator 为空。

---

如何将窗口的本地函数绑定到该窗口中包含的 UserControl 的 DependencyProperty？ 或者在这种特殊情况下：如何通过 xaml 设置 myUserControlInstance.FileValidator = ValidateMinFile？

Answer 1

UserControl1.xaml.cs

public delegate Tuple<bool, string> ExtraValidation(FileInfo fi);

public partial class UserControl1 : UserControl
{
    public UserControl1()
    {
        InitializeComponent();
    }

    #region FileValidator Property
    public ExtraValidation FileValidator
    {
        get { return (ExtraValidation)GetValue(FileValidatorProperty); }
        set { SetValue(FileValidatorProperty, value); }
    }

    public static readonly DependencyProperty FileValidatorProperty =
        DependencyProperty.Register(nameof(FileValidator), typeof(ExtraValidation), typeof(UserControl1),
            new PropertyMetadata(null, FileValidator_PropertyChanged));
    #endregion FileValidator Property

    protected static void FileValidator_PropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        //  I just put this here for testing: If it's non-null, it'll be called. 
        //  I set a breakpoint in the MainWindow method to detect the call. 
        (d as UserControl1).FileValidator?.Invoke(null);
    }
}

MainWindow.xaml.cs

    public MainWindow()
    {
        InitializeComponent();

        FileValidator = ValidateMinFile;
    }

    #region FileValidator Property
    public ExtraValidation FileValidator
    {
        get { return (ExtraValidation)GetValue(FileValidatorProperty); }
        set { SetValue(FileValidatorProperty, value); }
    }

    public static readonly DependencyProperty FileValidatorProperty =
        DependencyProperty.Register(nameof(FileValidator), typeof(ExtraValidation), typeof(MainWindow),
            new PropertyMetadata(null));
    #endregion FileValidator Property

    public Tuple<bool, string> ValidateMinFile(FileInfo f) // ExtraValidation delegate
    {
        //  Breakpoint here
        return new Tuple<bool, string>(false, "blah");
    }

MainWindow.xaml

    <local:UserControl1
        FileValidator="{Binding FileValidator, RelativeSource={RelativeSource AncestorType=Window}}"
        />

工作正常。