在wpf用户控件中访问控件的属性时出错 [英] error on accessing a property of a control in a wpf user control

问题描述

我用文本框和组合框创建了一个wpf用户控件. 为了访问文本框的text属性，我使用了以下代码

i have created a wpf user control with a text box and a combo box. for accessing the text property of the text box i have used the below code

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

public string TextBoxText
{
    get { return txtValue.Text; }
    set { txtValue.Text = value; }
}

在另一个项目中，我使用了控件并将文本绑定如下:

in another project i have used the control and bind the text as below:

<textboxunitconvertor:TextBoxUnitConvertor Name="wDValueControl" TextBoxText="{Binding _FlClass.SWa_SC.Value , RelativeSource={RelativeSource AncestorType=Window}, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"  Width="161" Height="28" HorizontalAlignment="Left" VerticalAlignment="Top"/>

我确定用于绑定的类可以正常工作，因为当我使用它直接在项目中与文本框bing时，它可以正常工作，但是当我将其绑定到usercontrol中的textbox的text属性时，它将带来null，并且绑定不起作用. 有人可以帮我吗?

i am certain that the class that is used for binding is properly working because when i used it to bing with a text box directly in my project it works properly but when i bind it to the text property of textbox in usercontrol it brings null and the binding does not work. can any one help me?

推荐答案

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 = ...
}

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