TextBox 绑定到 double 并输入小于 -1 的负数时的问题 [英] An issue when TextBox is binding to double and enter negative number that little than -1

问题描述

当我将文本框绑定到属性并输入小于 -1 的负数时遇到问题 - 例如 -0.45:

I have an issue when i binding a textbox to Propery and enter a negative number that is less than -1 - for example -0.45:

文本框:

<TextBox Text="{Binding Txt, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>

和财产:

  double txt;
    public double Txt
    {
        get { return txt; }
        set { txt = value; OnPropertyChanged("Txt"); }
    }

似乎当我尝试输入 -0.54 时它会立即更改为 0，为什么?

it seems when i try to enter -0.54 it changes immediatly to 0, why?

推荐答案

这是完成这项工作的转换器(所以保持你的视图模型原样 - 你可以将它用于十进制和双精度).我们只需要最初保留小数点和 -ve 位置:

Here is the convertor that does the job ( So leave your view model as it is- You can use it for both decimal and double). We just need to hold the decimal and -ve position initially:

 public class DecimalConverter:IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value !=null)
        {
            return value.ToString();
        }
        return Binding.DoNothing;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        string data = value as string;
        if (data == null)
        {
            return value;
        }
        if (data.Equals(string.Empty))
        {
            return 0;
        }
        if (!string.IsNullOrEmpty(data))
        {
            decimal result;
            //Hold the value if ending with .
            if (data.EndsWith(".") || data.Equals("-0"))
            {
                return Binding.DoNothing;
            }
            if (decimal.TryParse(data, out result))
            {
                return result;
            }
        }
        return Binding.DoNothing;
    }
}

所以我们持有值或在绑定时不做任何事情

So we hold the values or do nothing on binding

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