WinRT TextBox MaxLength 不将 \n\r 计为两个字符

Question

我将 TextBox 和 MaxLength 设置为 10，但当按下 Enter 键时它接受 11 个字符。看起来它正在将 \n\r 计为 1 个字符而不是两个。有没有办法让它把 \n\r 算作两个字符的长度？

Answer 1

如果您真的想在文本框中允许换行并限制其文本长度，我看到两个选项：

要么通过转换器绑定MaxLength，使其根据文本包含的换行符(\r\n)的数量改变其值，如this question

或者，您可以定义自己的附加属性 MaxLength 来正确计算文本长度。这可能看起来有点像以下内容（作为示例，您需要对其进行调整以考虑特殊情况等）：

public class TextBoxExtensions: DependencyObject
{
    public static readonly DependencyProperty MaxLengthProperty = DependencyProperty.RegisterAttached(
        "MaxLength", typeof (int), typeof (MaxLengthBehavior), new PropertyMetadata(default(int), PropertyChangedCallback));

    public static void SetMaxLength(DependencyObject element, int value)
    {
        element.SetValue(MaxLengthProperty, value);
    }

    public static int GetMaxLength(DependencyObject element)
    {
        return (int) element.GetValue(MaxLengthProperty);
    }

    private static void PropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs args)
    {
        var tb = dependencyObject as TextBox;
        if (tb != null)
        {
            tb.KeyDown -= TbOnKeyDown;
            tb.KeyDown += TbOnKeyDown;
        }
    }

    private static void TbOnKeyDown(object sender, KeyRoutedEventArgs args)
    {
        var tb = sender as TextBox;
        if (tb != null)
        {
            int max = GetMaxLength(tb);
            if (tb.Text.Length >= max)
                args.Handled = true;
        }
    }
}

<TextBox local:TextBoxExtensions.MaxLength="10" />

WinRT TextBox MaxLength 不将 \n\r 计为两个字符

WinRT TextBox MaxLength does not count \n\r as two characters

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