An issue when TextBox is binding to double and enter negative number that little than -1

Question

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:

the textbox:

Answer 1

when you enter the decimal value it becomes 0 again so the best way to do this is using the lostfocus trigger:

 <TextBox Text="{Binding Txt, Mode=TwoWay, UpdateSourceTrigger=LostFocus}"  Grid.Row="0"/>

Also you need to do this in the view model:

public double Txt
    {
        get { return txt; }
        set
        {
            if (!txt.Equals(value))
            {

                txt = value;
                OnPropertyChanged("Txt");
            }
        }
    }

Answer 2

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;
    }
}

So we hold the values or do nothing on binding