Utopia-Canteen-System/Converters/StringLengthToVisibilityConverter.cs

using System;
using System.Globalization;
using System.Windows;
using System.Windows.Data;

namespace UtopiaCanteenSystem.Converters
{
    public class StringLengthToVisibilityConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            // Binding is typically Text.Length (int): show watermark when empty (0), hide when has text
            if (value is int length)
                return length == 0 ? Visibility.Visible : Visibility.Collapsed;
            if (value is string s)
                return string.IsNullOrEmpty(s) ? Visibility.Visible : Visibility.Collapsed;
            return Visibility.Visible;
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return Binding.DoNothing; // No reverse conversion
        }
    }
}