.NET MAUI › Data Binding & MVVM

How do you implement value conversion in bindings?

Advanced

Answer

Implement IValueConverter (Convert and ConvertBack) to transform a source value into a target-friendly value, e.g., bool to color or enum to text. Declare the converter as a resource and reference it via Converter= in the binding. Use ConvertBack for two-way scenarios; return BindableProperty.UnsetValue to skip.

public class BoolToColorConverter : IValueConverter
{
    public object Convert(object v, Type t, object p, CultureInfo c)
        => (bool)v ? Colors.Green : Colors.Red;
    public object ConvertBack(object v, Type t, object p, CultureInfo c)
        => throw new NotSupportedException();
}

Real-world example A status dot turns green or red by binding IsOnline through a BoolToColorConverter, keeping the view model free of UI colors.

Common follow-ups: When do you need ConvertBack? | How do you pass a ConverterParameter?

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