WPF MVVM Textbox Validation

Question

I\'m creating a WPF application using MVVM. I have a textbox, which is bound to a property in my ViewModel of type double with a default value of 0.0. If I now ente

Answer 1

You can try following solution. Firstly you should declare DoubleProperty as Nullable:

    public double? DoubleProperty { get; set; }

Then create converter class implemented IValueConverter. It can looks like this:

 public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return value;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        double result;
        if(!double.TryParse((string)value, out result))
        {
            return null;
        }

        return result;
    }

Finally, you can use it:

    xmlns:converter="clr-namespace:[TestApplication]"


    

Now, if user typed wrong values - DoubleProperty will be null.