您的依赖项属性声明错误.它必须看起来如下所示，其中CLR属性包装器的getter和setter调用GetValue和SetValue方法:

Your dependency property declaration is wrong. It has to look like shown below, where the getter and setter of the CLR property wrapper call the GetValue and SetValue methods:

public static readonly DependencyProperty TextBoxTextProperty =
    DependencyProperty.Register(
        "TextBoxText", typeof(string), typeof(TextBoxUnitConvertor));

public string TextBoxText
{
    get { return (string)GetValue(TextBoxTextProperty); }
    set { SetValue(TextBoxTextProperty, value); }
}

在UserControl的XAML中，您将这样绑定到属性:

In the XAML of your UserControl, you would bind to the property like this:

<TextBox Text="{Binding TextBoxText,
    RelativeSource={RelativeSource AncestorType=UserControl}}" />

如果每当TextBoxText属性发生更改时需要通知，则可以使用传递给Register方法的PropertyMetadata来注册PropertyChangedCallback:

If you need to get notified whenever the TextBoxText property changes, you could register a PropertyChangedCallback with PropertyMetadata passed to the Register method:

public static readonly DependencyProperty TextBoxTextProperty =
    DependencyProperty.Register(
        "TextBoxText", typeof(string), typeof(TextBoxUnitConvertor),
        new PropertyMetadata(TextBoxTextPropertyChanged));

private static void TextBoxTextPropertyChanged(
    DependencyObject o, DependencyPropertyChangedEventArgs e)
{
    TextBoxUnitConvertor t = (TextBoxUnitConvertor)o;
    t.CurrentValue = ...
}