访问用户控件的元素

Question

我创建了一个UserControl,如下所示:

<UserControl
x:Class="MySample.MyControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:MySample"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300"
d:DesignWidth="400">

<Canvas>

    <Ellipse Width="150" Height="150"/>

    <TextBlock>Sample</TextBlock>

</Canvas>

现在,在我的主页面中,我想将用户控件中出现的文本从"Sample"更改为Hello World.所以,我在mainpage.xaml中这样做了

<local:MyControl x:Name="MyControl" Margin="100,50 0,0"></local:MyControl>

在我尝试引用MyControl的mainpage.xaml.cpp中,它似乎无法识别:

MainPage::MainPage(){MyControl->Text = "Hello World";}

任何的想法 ？

Answer 1

详细说明@Steven你的答案,在你的UserControl中定义一个DependencyProperty.定义DependencyProperty允许更改通知以触发对控件的更新.

在UserControl的代码隐藏中,您可以添加依赖项属性.

public partial class MyUserControl : UserControl
{
    public string TextBlockText
    {
        get { return (string)GetValue(TextBlockTextProperty); }
        set { SetValue(TextBlockTextProperty, value); }
    }

    public static readonly DependencyProperty TextBlockTextProperty =
        DependencyProperty.Register("TextBlockText", typeof(string), typeof(MyUserControl), new UIPropertyMetadata(""));


    public MyUserControl()
    {
        InitializeComponent();
        DataContext = this;
    }
}

这会暴露DependencyProperty您可以在UserControl的XAML中绑定的公共.

<UserControl>
        <TextBlock Text="{Binding Path=TextBlockText}" />
</UserControl>

现在,您需要一种从Window控件设置该属性的方法.我将详细介绍三种方法:

1.)由于TextBlockText属性在UserControl上公开,我们可以直接在XAML中设置它,如:

<Window x:Class="WpfApplication2.MainWindow"
  xmlns:local="clr-namespace:WpfApplication2">
  <local:MyUserControl TextBlockText="Text that you want to set.">
  </local:MyUserControl>
</Window>

2.)如果我们给UserControl一个名字,我们可以改变Window代码隐藏中的属性:

<Window x:Class="WpfApplication2.MainWindow"
  xmlns:local="clr-namespace:WpfApplication2">
  <local:MyUserControl Name="CoolUserControl">
  </local:MyUserControl>
</Window>

-

CoolUserControl.TextBlockText = "Text that you want to set.";

3.)或者最后你可以DependencyProperty在你Window的代码隐藏中创建另一个并将它绑定到UserControl的依赖属性.这样,每当您更新属性时Window代码中的值UserControl依赖项属性也会更改.这是最好的选择@Steven你之前说过,因为你的代码背后不需要知道任何控件.

public partial class MainWindow : Window
{

    public string UserControlText
    {
        get { return (string)GetValue(UserControlTextProperty); }
        set { SetValue(UserControlTextProperty, value); }
    }

    public static readonly DependencyProperty UserControlTextProperty =
        DependencyProperty.Register("UserControlText", typeof(string), typeof(MainWindow), new UIPropertyMetadata(""));


    public MainWindow()
    {
        InitializeComponent();
        DataContext = this;
        UserControlText = "Text that you want to set.";
    }
}

并绑定到我们DependencyProperty在Window XAML中的新功能:

<Window x:Class="WpfApplication2.MainWindow"
        xmlns:local="clr-namespace:WpfApplication2">
    <local:MyUserControl TextBlockText="{Binding RelativeSource={RelativeSource AncestorType={x:Type Window}, Mode=FindAncestor}, Path=UserControlText}"></local:MyUserControl>
</Window>

希望这可以帮助!