Storing decimal numbers in double? property using updatesourcetrigger as PropertyChanged

Question

I am using WPF/MVVM. I am binding a textbox.Text to a nullable double in view model. UpdateSourceTrigger = PropertyChanged and not Lostfocus. Hence the double property will be updated when each digit is entered using Double.Parse(textbox.Text) inside the converter I am using. I am using PropertyChanged and converter here since I need to do some other validation checks.

My issue is I need to enter "1.69". When I enter "1", it is added as "1" to the property. Next I enter ".", but it is not added as "1." since double.parse saves the number as "1"

So I can't add decimal numbers. Please help. Thanks in advance.

Answer 1

You should be fine, if you use StringFormat=\{0:n\}. For example:

<TextBox Text="{Binding FooValue, UpdateSourceTrigger=PropertyChanged, 
                                               StringFormat=\{0:n\}}"/>

or just use a converter. For example:

<Window.Resources>        
   <helper:DoubleConverter x:Key="DoubleConverter" />
</Window.Resources>
...The code omitted for the brevity
<TextBox Text="{Binding Amount, UpdateSourceTrigger=PropertyChanged,       
                        Converter={StaticResource DoubleConverter}}"/>

and DoubleConverter:

public class DoubleConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
       return value;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
       // return an invalid value in case of the value ends with a point
       return value.ToString().EndsWith(".") ? "." : value;
    }
}