WPF用户控件双TextBox交互需求：选只读框文本时可编辑框仍能键盘输入

要实现「选只读TextBox文本时仍能在可编辑TextBox键盘输入」的需求，核心是让只读TextBox响应鼠标选择但不抢夺键盘焦点，具体实现如下：

1. XAML设置 #

给两个TextBox绑定鼠标事件：

<StackPanel>
    <TextBox 
        x:Name="readOnlyTextbox" 
        IsReadOnly="True" 
        PreviewMouseDown="ReadOnlyTextbox_PreviewMouseDown"
        PreviewMouseMove="ReadOnlyTextbox_PreviewMouseMove"
        PreviewMouseUp="ReadOnlyTextbox_PreviewMouseUp"/>
    <TextBox 
        x:Name="editableTextbox" 
        Margin="0,10,0,0"/>
</StackPanel>

2. 后台事件处理 #

通过拦截鼠标事件实现文本选择，同时阻止只读TextBox获取焦点：

private bool _isSelecting;

private void ReadOnlyTextbox_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
    var textBox = sender as TextBox;
    if (textBox == null) return;

    _isSelecting = true;
    e.Handled = true; // 阻止焦点转移到只读TextBox

    // 初始化点击位置的选择起点
    var charIndex = textBox.GetCharacterIndexFromPoint(e.GetPosition(textBox), true);
    if (charIndex >= 0)
    {
        textBox.SelectionStart = charIndex;
        textBox.SelectionLength = 0;
    }
}

private void ReadOnlyTextbox_PreviewMouseMove(object sender, MouseEventArgs e)
{
    var textBox = sender as TextBox;
    if (!_isSelecting || e.LeftButton != MouseButtonState.Pressed || textBox == null)
        return;

    // 拖动时更新选择范围
    var charIndex = textBox.GetCharacterIndexFromPoint(e.GetPosition(textBox), true);
    if (charIndex >= 0)
    {
        textBox.SelectionLength = charIndex - textBox.SelectionStart;
    }
}

private void ReadOnlyTextbox_PreviewMouseUp(object sender, MouseButtonEventArgs e)
{
    _isSelecting = false;
}

3. 初始化可编辑TextBox焦点 #

保留你的初始化逻辑，确保控件加载时可编辑TextBox获得焦点：

public YourUserControl()
{
    InitializeComponent();
    Loaded += (s, e) =>
    {
        editableTextbox.CaretIndex = editableTextbox.Text.Length;
        editableTextbox.Focus();
    };
}

效果 #

• 只读TextBox可正常用鼠标选文本，不会夺走可编辑TextBox的键盘焦点；
• 键盘输入始终直接进入可编辑TextBox，无需手动切换；
• 文本选择交互和原生TextBox一致，用户体验无断层。

内容的提问来源于stack exchange，提问作者Hina