从 XAML 访问间接属性 - WPF

Question

I have a Control class named MyControl and it has direct bool property AccessDirectProperty and an Object MyControlSettings

    public class MyControl : Control
    {
        public bool AccessDirectProperty
        {
            get; set;
        }
        public MyControlSettings ControlSettings
        {
            get;set;
        }
    }

Please find the MyControlSettings class details

public class MyControlSettings
{
    public bool AccessIndirectProperty
    {
        get;set;
    }
}

Direct property AccessDirectProperty can be accessible from XAML without any error.

<Window>
    <Grid>
        <local:MyControl AccessDirectProperty="True"/>
    </Grid>
</Window>

But I cannot access the property AccessIndirectProperty from the object ControlSettings in XAML. The below code fails to do that.

<Window>
    <Grid>
        <local:MyControl AccessDirectProperty="True" ControlSettings.AccessIndirectProperty=""/>
    </Grid>
</Window>

Can anyone help me on this?

Answer 1

I'm afraid that XAML does not support accessing "nested" properties.

You could, however, make ControlSettings an independent class with attached properties :

public class ControlSettings : DependencyObject
{
    public static readonly DependencyProperty AccessIndirectPropertyProperty =
        DependencyProperty.RegisterAttached(
              "AccessIndirectProperty", typeof(bool), typeof(ControlSettings),
              new PropertyMetadata(false));

    public static bool GetAccessIndirectProperty(DependencyObject d)
    {
        return (bool) d.GetValue(AccessIndirectPropertyProperty);
    }
    public static void SetAccessIndirectProperty(DependencyObject d, bool value)
    {
        d.SetValue(AccessIndirectPropertyProperty, value);
    }
}

Then,

<local:MyControl x:Name="myControl" 
                 AccessDirectProperty="True" 
                 ControlSettings.AccessIndirectProperty="True" />

would set a value which could be accessed via

var p = ControlSettings.GetAccessIndirectProperty(myControl); // yields True

Answer 2

Now, on a technical level, the following is not useful to modify a property of an existing MyControlSettings instance provided through MyControl.ControlSettings . However, if your use case allows creating and assigning an entirely new MyControlSettings instance to MyControl.ControlSettings , you can do so in XAML:

<local:MyControl>
    <ControlSettings>
        <local:MyControlSettings AccessIndirectProperty="true" />
    </ControlSettings>
</local:MyControl>

A side note: The term " ControlSettings " suggest to me that you want to kind of "package" control settings/properties in some kind of MyControlSettings "container". Now, i don't know why and what the motivation for this is, but keep in mind that choosing this approach can make it very hard or even impossible to use data bindings in a meaningful way where such a settings property is supposed to be the binding target. If you want to be able to use individual settings as binding target (like AccessIndirectProperty="{Binding Path=Source}" ), i would rather suggest your MyControl exposes those settings individually as DependencyProperties .