如何正确将模型中的字符串绑定到 WPF 中的 TextBox？

huangapple
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英文:

How do I correctly bind a string in my model to an TextBox in WPF?

问题

我遇到了绑定错误，例如：

System.Windows.Data Error: 40 : BindingExpression 路径错误：在“object” “String” 上找不到“MyText”属性 (HashCode=-401799582)。 BindingExpression:Path=MyText; DataItem=“String” (HashCode=-401799582); 目标元素为“TextBox” (Name=“”); 目标属性为“Text” (类型“String”)

当尝试将我的模型的字符串属性绑定到TextBox和TextBlock时（上面的错误是TextBox的错误）。

我尝试松散地按照Microsoft网站上的 教程 进行操作。

在XAML中：

  1. <Window x:Class="WpfApp1.MainWindow"
  2.         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  3.         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  4.         xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
  5.         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
  6.         xmlns:src="clr-namespace:WpfApp1"
  7.         mc:Ignorable="d"
  8.         Title="MainWindow" Height="450" Width="800">
  9.     <Window.Resources>
  10.         <src:MyView x:Key="myView"/>
  11.     </Window.Resources>
  12.     <Grid>
  13.         <StackPanel>
  14.             <Label>Input:</Label>
  15.             <TextBox>
  16.                 <TextBox.Text>
  17.                     <Binding Source="{StaticResource myView}" Path="MyText" UpdateSourceTrigger="PropertyChanged"/>
  18.                 </TextBox.Text>
  19.             </TextBox>
  20.             <Label>In model:</Label>
  21.             <TextBlock>
  22.                 <TextBlock.Text>
  23.                     <Binding Source="{StaticResource myView}" Path="MyText"/>
  24.                 </TextBlock.Text>
  25.             </TextBlock>
  26.         </StackPanel>
  27.     </Grid>
  28. </Window>

在C#中：

  1. using System.ComponentModel;
  2. using System.Windows;
  4. namespace WpfApp1
  5. {
  6.     public class MyView : INotifyPropertyChanged
  7.     {
  8.         public MyView() { }
  9.         public event PropertyChangedEventHandler PropertyChanged;
  10.         private string _myText;
  11.         public string MyText
  12.         {
  13.             set
  14.             {
  15.                 if (_myText != value)
  16.                 {
  17.                     _myText = value;
  18.                     PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("MyText"));
  19.                 }
  20.             }
  21.             get { return _myText;  }
  22.         }
  23.     }
  25.     public partial class MainWindow : Window
  26.     {
  27.         public MainWindow()
  28.         {
  29.             InitializeComponent();
  30.         }
  31.     }
  32. }

我期望TextBlock在我在TextBox中输入文本时显示文本，但实际上没有任何反应（这是因为存在绑定错误）。我做错了什么？

英文:

I'm getting the binding errors, e.g.

> System.Windows.Data Error: 40 : BindingExpression path error: 'MyText' property not found on 'object' ''String' (HashCode=-401799582)'. BindingExpression:Path=MyText; DataItem='String' (HashCode=-401799582); target element is 'TextBox' (Name=''); target property is 'Text' (type 'String')

When trying to bind a string property of my model to a TextBox and a TextBlock (the error above is the one for the TextBox).

I've tried loosely following the how-to in Microsoft's site.

in xaml:

  2. &lt;Window x:Class=&quot;WpfApp1.MainWindow&quot;
  3.         xmlns=&quot;http://schemas.microsoft.com/winfx/2006/xaml/presentation&quot;
  4.         xmlns:x=&quot;http://schemas.microsoft.com/winfx/2006/xaml&quot;
  5.         xmlns:d=&quot;http://schemas.microsoft.com/expression/blend/2008&quot;
  6.         xmlns:mc=&quot;http://schemas.openxmlformats.org/markup-compatibility/2006&quot;
  7.         xmlns:src=&quot;clr-namespace:WpfApp1&quot;
  8.         mc:Ignorable=&quot;d&quot;
  9.         Title=&quot;MainWindow&quot; Height=&quot;450&quot; Width=&quot;800&quot;&gt;
  10.     &lt;Window.Resources&gt;
  11.         &lt;src:MyView x:Key=&quot;myView&quot;/&gt;
  12.     &lt;/Window.Resources&gt;
  13.     &lt;Grid&gt;
  14.         &lt;StackPanel&gt;
  15.             &lt;Label&gt;Input:&lt;/Label&gt;
  16.             &lt;TextBox&gt;
  17.                 &lt;TextBox.Text&gt;
  18.                     &lt;Binding Source=&quot;StaticResource myView&quot; Path=&quot;MyText&quot; UpdateSourceTrigger=&quot;PropertyChanged&quot;/&gt;
  19.                 &lt;/TextBox.Text&gt;
  20.             &lt;/TextBox&gt;
  21.             &lt;Label&gt;In model:&lt;/Label&gt;
  22.                 &lt;TextBlock&gt;
  23.                 &lt;TextBlock.Text&gt;
  24.                     &lt;Binding Source=&quot;StaticResource myView&quot; Path=&quot;MyText&quot;/&gt;
  25.                 &lt;/TextBlock.Text&gt;
  26.                 &lt;/TextBlock&gt;
  27.         &lt;/StackPanel&gt;
  28.     &lt;/Grid&gt;
  29. &lt;/Window&gt;

in C#:

  2. using System.ComponentModel;
  3. using System.Windows;
  6. namespace WpfApp1
  7. {
  8.     public class MyView : INotifyPropertyChanged
  9.     {
  10.         public MyView() { }
  11.         public event PropertyChangedEventHandler PropertyChanged;
  12.         private string _myText;
  13.         public string MyText
  14.         {
  15.             set
  16.             {
  17.                 if (_myText != value)
  18.                 {
  19.                     _myText = value;
  20.                     PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(&quot;MyText&quot;));
  21.                 }
  22.             }
  23.             get { return _myText;  }
  24.         }
  26.     }
  28.     public partial class MainWindow : Window
  29.     {
  30.         public MainWindow()
  31.         {
  32.             InitializeComponent();
  33.         }
  34.     }
  35. }

I was expecting the TextBlock to display my text as I type it in the TextBox, but it runs and nothing happens (which makes sense seeing as there was a binding error).

What Am I doing wrong?

答案1

得分: 1

在字符串中编写StaticResource并不意味着您已引用该资源。StaticResource 是一个标记扩展，具有自己的语法（花括号）：

  1. <StackPanel>
  2.     <Label>Input:</Label>
  3.     <TextBox>
  4.         <TextBox.Text>
  5.             <Binding Source="{StaticResource myView}" Path="MyText" UpdateSourceTrigger="PropertyChanged"/>
  6.         </TextBox.Text>
  7.     </TextBox>
  9.     <Label>In model:</Label>
  10.     <TextBlock>
  11.         <TextBlock.Text>
  12.             <Binding Source="{StaticResource myView}" Path="MyText"/>
  13.         </TextBlock.Text>
  14.     </TextBlock>
  15. </StackPanel>

您还可以以更简洁的方式编写相同的标记：

  1. <StackPanel>
  2.     <Label>Input:</Label>
  3.     <TextBox Text="{Binding Path=MyText, Source={StaticResource myView}, UpdateSourceTrigger=PropertyChanged}"/>
  5.     <Label>In model:</Label>
  6.     <TextBlock Text="{Binding Path=MyText, Source={StaticResource myView}}"/>
  7. </StackPanel>

或者甚至更好 - 声明 DataContext，而不是资源：

  1. <Window x:Class="WpfApp1.MainWindow"
  2.     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  3.     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  4.     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
  5.     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
  6.     xmlns:src="clr-namespace:WpfApp1"
  7.     mc:Ignorable="d"
  8.     Title="MainWindow" Height="450" Width="800">
  9.     <Window.DataContext>
  10.         <src:MyView />
  11.     </Window.DataContext>
  12.     <Grid>
  13.         <StackPanel>
  14.             <Label>Input:</Label>
  15.             <TextBox Text="{Binding MyText, UpdateSourceTrigger=PropertyChanged}"/>
  17.             <Label>In model:</Label>
  18.             <TextBlock Text="{Binding MyText}"/>
  19.         </StackPanel>
  20.     </Grid>
  21. </Window>
英文:

writing StaticResource in a string doesn't mean that you referenced that resource. StaticResource is a markup extension and has its own syntax (curly braces):

  1. &lt;StackPanel&gt;
  2.     &lt;Label&gt;Input:&lt;/Label&gt;
  3.     &lt;TextBox&gt;
  4.         &lt;TextBox.Text&gt;
  5.             &lt;Binding Source=&quot;{StaticResource myView}&quot; Path=&quot;MyText&quot; UpdateSourceTrigger=&quot;PropertyChanged&quot;/&gt;
  6.         &lt;/TextBox.Text&gt;
  7.     &lt;/TextBox&gt;
  9.     &lt;Label&gt;In model:&lt;/Label&gt;
  10.     &lt;TextBlock&gt;
  11.         &lt;TextBlock.Text&gt;
  12.             &lt;Binding Source=&quot;{StaticResource myView}&quot; Path=&quot;MyText&quot;/&gt;
  13.         &lt;/TextBlock.Text&gt;
  14.     &lt;/TextBlock&gt;
  15. &lt;/StackPanel&gt;

you can also write the same markup in significantly less verbose way:

  1. &lt;StackPanel&gt;
  2.     &lt;Label&gt;Input:&lt;/Label&gt;
  3.     &lt;TextBox Text=&quot;{Binding Path=MyText, Source={StaticResource myView}, UpdateSourceTrigger=PropertyChanged}&quot;/&gt;
  5.     &lt;Label&gt;In model:&lt;/Label&gt;
  6.     &lt;TextBlock Text=&quot;{Binding Path=MyText, Source={StaticResource myView}}&quot;/&gt;
  7. &lt;/StackPanel&gt;

or even better - declare DataContext, not a Resource:

  1. &lt;Window x:Class=&quot;WpfApp1.MainWindow&quot;
  2.     xmlns=&quot;http://schemas.microsoft.com/winfx/2006/xaml/presentation&quot;
  3.     xmlns:x=&quot;http://schemas.microsoft.com/winfx/2006/xaml&quot;
  4.     xmlns:d=&quot;http://schemas.microsoft.com/expression/blend/2008&quot;
  5.     xmlns:mc=&quot;http://schemas.openxmlformats.org/markup-compatibility/2006&quot;
  6.     xmlns:src=&quot;clr-namespace:WpfApp1&quot;
  7.     mc:Ignorable=&quot;d&quot;
  8.     Title=&quot;MainWindow&quot; Height=&quot;450&quot; Width=&quot;800&quot;&gt;
  9.     &lt;Window.DataContext&gt;
  10.         &lt;src:MyView /&gt;
  11.     &lt;/Window.DataContext&gt;
  12.     &lt;Grid&gt;
  13.         &lt;StackPanel&gt;
  14.             &lt;Label&gt;Input:&lt;/Label&gt;
  15.             &lt;TextBox Text=&quot;{Binding MyText, UpdateSourceTrigger=PropertyChanged}&quot;/&gt;
  16.     
  17.             &lt;Label&gt;In model:&lt;/Label&gt;
  18.             &lt;TextBlock Text=&quot;{Binding MyText}&quot;/&gt;
  19.          &lt;/StackPanel&gt;
  20.     &lt;/Grid&gt;
  21. &lt;/Window&gt;

huangapple
  • 本文由 发表于 2023年2月19日 20:56:23
  • 转载请务必保留本文链接：https://go.coder-hub.com/75500293.html
  • c#
  • data-binding
  • wpf
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