Xamarin.forms Converters

BooleanToYesNoConverter.cs

public class BooleanToYesNoConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return (bool)value ? AppResources.BtnYes : AppResources.BtnNo;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return (bool)value ? AppResources.BtnYes : AppResources.BtnNo;
    }
}

HasDataConverter.cs

public class HasDataConverter : IValueConverter
{
    /// <summary>
    /// Init this instance.
    /// </summary>
    public static void Init()
    {
        DateTime time = DateTime.UtcNow;
    }

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        //if null then not visible
        if (value == null)
            return false;

        //if empty string then not visible
        if (value is string)
            return !string.IsNullOrWhiteSpace((string)value);

        //if blank list not visible
        if (value is IList)
            return ((IList)value).Count > 0;

        return true;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

ListHeightConverter.cs

public class ListHeightConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value == null)
            return 0;

        return (int)value * int.Parse(parameter.ToString());
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value == null)
            return 0;

        return (int)value * int.Parse(parameter.ToString());
    }
}

ListNullOrEmptyBoolConverter.cs

public class ListNullOrEmptyBoolConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value is ICollection collection && collection.Count > 0;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value is ICollection collection && collection.Count > 0;
    }
}

NegateBooleanConverter.cs

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

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return !(bool)value;
    }
}

PropertyValueStringConverter.cs

public class PropertyValueStringConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return value.ToString();
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

ValueConverterGroup.cs

public class ValueConverterGroup : List<IValueConverter>, IValueConverter
{
    private string[] _parameters;

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (parameter != null)
            _parameters = Regex.Split(parameter.ToString(), @"(?<!\\),");

        return (this).Aggregate(value, (current, converter) => converter.Convert(current, targetType, GetParameter(converter), culture));
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }

    private string GetParameter(IValueConverter converter)
    {
        if (_parameters == null)
            return null;

        int index = IndexOf(converter);
        string parameter;

        try
        {
            parameter = _parameters[index];
        }
        catch (IndexOutOfRangeException ex)
        {
            parameter = null;
        }

        if (parameter != null)
            parameter = Regex.Unescape(parameter);

        return parameter;
    }
}