我无法将数据绑定到WPF/XAML中的局部变量

Question

我想要一个文本框在我点击它时显示变量的值(迭代次数为1到100),我不知道我在做什么错误:

当我运行项目时,文本框中不显示任何内容.

在文本框中显示变量的最佳方法是什么？

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace dataBindingTest
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        public string myText { get; set; }

        public void Button_Click_1(object sender, RoutedEventArgs e)
        {
            int i = 0;
            for (i = 0; i < 100; i++)
            {
                myText = i.ToString();
            }
        }
    }
}

XAML:

<Window x:Class="dataBindingTest.MainWindow"
        Name="windowElement"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Button Content="Button" HorizontalAlignment="Left" Height="106" Margin="71,95,0,0" VerticalAlignment="Top" Width="125" Click="Button_Click_1"/>
        <TextBlock x:Name="myTextBox" HorizontalAlignment="Left" Height="106" Margin="270,95,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="187" Text= "{Binding myText, ElementName=windowElement}" />

    </Grid>
</Window>

Answer 1

myText当您的值已更改时,您当前的属性无法通知WPF绑定系统,因此TextBlock不会更新.

如果您将其设为依赖项属性,则会自动实现更改通知,并且对该属性的更改将反映在该属性中TextBlock.

因此,如果您替换public string myText { get; set; }所有这些代码,它应该工作:

public string myText
{
    get { return (string)GetValue(myTextProperty); }
    set { SetValue(myTextProperty, value); }
}

// Using a DependencyProperty as the backing store for myText.  This enables animation, styling, binding, etc...
public static readonly DependencyProperty myTextProperty =
    DependencyProperty.Register("myText", typeof(string), typeof(Window1), new PropertyMetadata(null));

Answer 2

实施INotifyPropertyChanged:

public partial class MainWindow : Window, INotifyPropertyChanged
    {
        public MainWindow()
        {
            this.InitializeComponent();
        }

        private string _txt;
        public string txt
        {
            get
            {
                return _txt;
            }
            set
            {
                if (_txt != value)
                {
                    _txt = value;
                    OnPropertyChanged("txt");
                }
            }
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            txt = "changed text";
        }

        public event PropertyChangedEventHandler PropertyChanged;

        protected void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }

XAML:

<TextBox Text="{Binding txt}"/>
<Button Click="Button_Click">yes</Button>

并且不要忘记添加窗口的DataContext属性:

<Window ... DataContext="{Binding RelativeSource={RelativeSource Self}}"/>