wpf - 在wpf中绑定时如何使自定义的依赖属性可以实时更改？

Question

当我们像这样将 textblock.Text 与 Textbox 的文本长度绑定时

<TextBox x:Name="txtName" Grid.Row="0" />
<TextBlock Text="{Binding ElementName=txtName, Path=Text.Length}" Grid.Row="1" />

Textblock 的 Text 会随着 txtName 的文本实时变化。但是当我在 WPF 用户控件中定义一个新的 DependencyProperty 时，如下所示：

    //MyCustomUC.xaml.cs
    static FrameworkPropertyMetadata propertymetadata = new FrameworkPropertyMetadata("Comes as Default", FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, new PropertyChangedCallback(MyCustom_PropertyChanged), new CoerceValueCallback(MyCustom_CoerceValue), false, UpdateSourceTrigger.PropertyChanged);

    public static readonly DependencyProperty MyCustomProperty = DependencyProperty.Register("MyCustom", typeof(string), typeof(MyCustomUC), propertymetadata, new ValidateValueCallback(MyCustom_Validate));

    public string MyCustom
    {
        get
        {
            return this.GetValue(MyCustomProperty) as string;
        }
        set
        {
            this.SetValue(MyCustomProperty, value);
        }
    }

并将其绑定到文本框

//MyCustomUC.xaml
<UserControl ... x:Name="ucs" ...>
<TextBox Text="{Binding ElementName=ucs, Path=MyCustom}"></TextBox>
</UserControl>

//MainWindow.xaml
<local:MyCustomUC x:Name="ucust" Grid.Row="0" />
<TextBox x:Name="tbChange" Text="{Binding ElementName=ucust, Path=MyCustom}" Grid.Row="1"/>

在文本框失去焦点之前，似乎“MyCustom”不会改变。当文本框中的文本实时更改时，如何更改它？先感谢您。

Answer 1

<TextBox x:Name="tbChange" Text="{Binding ElementName=ucust, Path=MyCustom, UpdateSourceTrigger=PropertyChanged}" Grid.Row="1"/>