No property, bindable property, or event found for 'Converter', or mismatching type between

No property, bindable property, or event found for 'Converter', or mismatching type between value and property.

There is my code:

and controls:LabelIem code:

    #region RightText：右文字
    public static readonly BindableProperty RightTextProperty = BindableProperty.Create(nameof(RightText), typeof(string), typeof(LabelItem), null, propertyChanged: OnRightTextChanged);

    private static void OnRightTextChanged(BindableObject bindable, object oldValue, object newValue)
    {
        string text = newValue as string;
        var label = (LabelItem)bindable;
        label.LabelRight.Text = text;
    }

    public string RightText
    {
        get { return (string)GetValue(RightTextProperty); }
        set { SetValue(RightTextProperty, value); }
    }
    #endregion

then SexConverter definition:
///

/// 格式化性别
///

public class SexConverter : IValueConverter
{
///

/// 在绑定模式为OneWay或TwoWay时，数据由源流向目标时调用，
///

///

///
///
///
///
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (!(value is int?))
{
throw new InvalidNavigationException("The target must be a boolean");
}

        return ((int)value == 1) ? "男" : "女";
    }

    /// <summary>
    /// 在绑定模式为TwoWay或OneWayToSource时数据由目标流向源时调用
    /// </summary>
    /// <param name="value"></param>
    /// <param name="targetType"></param>
    /// <param name="parameter"></param>
    /// <param name="culture"></param>
    /// <returns></returns>
    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return null;
    }
}

Why compile is wrong??::
No property, bindable property, or event found for 'Converter', or mismatching type between value and property.

The error occurred:
RightText="{Binding Model.Sex,Converter={Binding SexConverter}}"

thanks