格式化后奇怪的文本框插入符号行为

Question

我已经编写了简单的WPF自定义textbox控件来保存十进制值。以下是其代码的一个非常“轻量级”的版本，没有大部分方法和属性(但对于测试来说应该足够了)：

using System;
using System.Globalization;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;

namespace CustomControls
{
    public class NumericBox : TextBox
    {
        public static readonly DependencyProperty ValueProperty;
        public static readonly DependencyProperty DecimalCountProperty;

        static NumericBox()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(NumericBox), new FrameworkPropertyMetadata(typeof(NumericBox)));
            ValueProperty = DependencyProperty.Register("Value", typeof (decimal?), typeof (NumericBox),
                new FrameworkPropertyMetadata(0m, OnValueChanged));
            DecimalCountProperty = DependencyProperty.Register("DecimalCount", typeof(int), typeof(NumericBox),
                new FrameworkPropertyMetadata(2, OnDecimalCountChanged));

        }
        public int DecimalCount
        {
            get { return (int)GetValue(DecimalCountProperty); }
            set { SetValue(DecimalCountProperty, value); }
        }
        public decimal? Value
        {
            get { return (decimal?)GetValue(ValueProperty); }
            set { SetValue(ValueProperty, value); }
        }
        private static void OnValueChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
        }
        private static void OnDecimalCountChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
        }
        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            BindingOperations.ClearAllBindings(this);
            var textBinding = new Binding("Value")
            {
                Converter = new TextToNumericBoxValueConverter(),
                Mode = BindingMode.TwoWay,
                UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged,
                RelativeSource = new RelativeSource(RelativeSourceMode.Self),
                ConverterParameter = DecimalCount
            };
            SetBinding(TextProperty, textBinding);
        }
    }

    public class TextToNumericBoxValueConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            var d = value as decimal?;
            if (d == null) return "";
            var p = parameter is int ? (int)parameter : 0;
            var nf = culture.NumberFormat.Clone() as NumberFormatInfo;
            if (nf == null) return "";
            nf.NumberDecimalDigits = p;
            return d.Value.ToString("N", nf);
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            decimal d;
            var s = value as string;
            if (s == null)
                return null;
            if (decimal.TryParse(s, out d))
                return d;
            return null;
        }
    }
}

现在，奇怪的事情开始了。如果我连续输入几个相同的数字，那么在输入第10个数字之前，一切都是正常的。然后插入符号跳到第5个位置。这是在2位小数的情况下。比方说，如果是3位十进制数字，在第11次击键后，插入符号会跳到第6位。如果我键入不同的数字，插入符号会跳到文本的末尾。如果格式中没有小数位，则一切正常。我尝试过手动设置格式，但没有成功。下面是一个小插图：

​

Answer 1

如果要将插入符号移到小数点之前，请尝试执行以下操作：

this.CaretIndex = string.Substring(0, this.Text.IndexOf(".")).Length;

• 如果上面的代码将插入符号移动到小数点后，则将其更改为：

this.CaretIndex = string.Substring(0, this.Text.IndexOf(".") - 1).Length;

如果要将插入符号移动到框的开头：

this.CaretIndex = 0;

如果要将插入符号移动到框的末尾：

this.CaretIndex = this.Text.Length;