In some cases, there are times when we need to data bind two properties of incompatible types. A Converter is an object that converts the value from source to target and vice versa. Each converter must implement the IValueConverter interface, which implements two functions, Convert and ConvetBack. We are going to create a converter that will take a bool as the source, and simply return the opposite value to the value in the source.

The ConvertBack method will only be used if the data binding is a TwoWay binding.

In the Stocklist.XamForms project, add a new folder called Converters, and inside this folder create a new file called NotConverter.cs, implement the following:

    public class NotConverter : IValueConverter 
    { 
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) 
        { 
            var b = value as bool?; 
 
            if (b != null) 
            { 
...