如何在多个XAML文件的TextBox中复用同一个OnTextChanged方法

下面提供几种无需复制代码即可在多个XAML文件中共享OnTextChanged逻辑的方案：

方案1：使用附加属性 #

创建静态辅助类，将文本处理逻辑封装为附加属性，通过XAML直接给TextBox启用该功能：

using System.Windows;
using System.Windows.Controls;

public static class TextBoxInputHelper
{
    // 定义附加属性，标记是否启用逗号转句号功能
    public static readonly DependencyProperty ReplaceCommaWithPeriodProperty =
        DependencyProperty.RegisterAttached(
            "ReplaceCommaWithPeriod",
            typeof(bool),
            typeof(TextBoxInputHelper),
            new PropertyMetadata(false, OnReplaceCommaWithPeriodChanged));

    public static void SetReplaceCommaWithPeriod(TextBox element, bool value)
    {
        element.SetValue(ReplaceCommaWithPeriodProperty, value);
    }

    public static bool GetReplaceCommaWithPeriod(TextBox element)
    {
        return (bool)element.GetValue(ReplaceCommaWithPeriodProperty);
    }

    private static void OnReplaceCommaWithPeriodChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (d is TextBox textBox)
        {
            if ((bool)e.NewValue)
            {
                textBox.TextChanged += OnTextBoxTextChanged;
            }
            else
            {
                textBox.TextChanged -= OnTextBoxTextChanged;
            }
        }
    }

    // 共享的文本处理逻辑
    private static void OnTextBoxTextChanged(object sender, TextChangedEventArgs e)
    {
        if (sender is TextBox myInput)
        {
            // 避免递归触发TextChanged
            myInput.TextChanged -= OnTextBoxTextChanged;
            
            myInput.Text = myInput.Text.Replace(",", ".").Trim();
            myInput.CaretIndex = myInput.Text.Length;
            
            myInput.TextChanged += OnTextBoxTextChanged;
        }
    }
}

在XAML中使用时，先引入对应命名空间（假设辅助类在YourNamespace.Helpers下）：

xmlns:helpers="clr-namespace:YourNamespace.Helpers"

然后给TextBox设置附加属性：

<TextBox helpers:TextBoxInputHelper.ReplaceCommaWithPeriod="True"/>

方案2：使用Blend行为 #

如果项目已引用Microsoft.Xaml.Behaviors.Wpf（可通过NuGet安装），可以封装为行为，更符合MVVM风格：

using Microsoft.Xaml.Behaviors;
using System.Windows.Controls;

public class ReplaceCommaWithPeriodBehavior : Behavior<TextBox>
{
    protected override void OnAttached()
    {
        base.OnAttached();
        AssociatedObject.TextChanged += OnTextChanged;
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();
        AssociatedObject.TextChanged -= OnTextChanged;
    }

    private void OnTextChanged(object sender, TextChangedEventArgs e)
    {
        if (sender is TextBox myInput)
        {
            myInput.TextChanged -= OnTextChanged;
            
            myInput.Text = myInput.Text.Replace(",", ".").Trim();
            myInput.CaretIndex = myInput.Text.Length;
            
            myInput.TextChanged += OnTextChanged;
        }
    }
}

XAML中使用：

xmlns:i="http://schemas.microsoft.com/xaml/behaviors"
xmlns:behaviors="clr-namespace:YourNamespace.Behaviors"

<TextBox>
    <i:Interaction.Behaviors>
        <behaviors:ReplaceCommaWithPeriodBehavior/>
    </i:Interaction.Behaviors>
</TextBox>

方案3：继承页面基类 #

如果所有使用该TextBox的页面都可以继承同一个自定义基页面，可将逻辑放在基类中：

using System.Windows;
using System.Windows.Controls;

public class BasePage : Window // 若为UserControl则继承UserControl
{
    protected void OnTextChanged(object sender, TextChangedEventArgs e)
    {
        var myInput = sender as TextBox;
        if (myInput == null) return;
        
        myInput.Text = myInput.Text.Replace(",", ".").Trim();
        myInput.CaretIndex = myInput.Text.Length;
    }
}

然后让你的页面继承这个基类：

public partial class YourPage : BasePage
{
    public YourPage()
    {
        InitializeComponent();
    }
}

对应的XAML根节点也要修改：

<helpers:BasePage x:Class="YourNamespace.YourPage"
                  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                  xmlns:helpers="clr-namespace:YourNamespace.Helpers">
    <!-- 页面内容 -->
    <TextBox TextChanged="OnTextChanged"/>
</helpers:BasePage>

内容的提问来源于stack exchange，提问作者online123