using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using FWindSoft.Wpf;

namespace FWindSoft.Wpf.Selector
{
    public interface IEmptyTemplateChecker
    {
        bool IsEmpty(object item);
    }

    public class DefaultEmptyTemplateChecker : IEmptyTemplateChecker
    {
        public bool IsEmpty(object item)
        {
            return item == null;
        }
    }
    /// <summary>
    /// 空模板选择类
    /// </summary>
    public class EmptyDataTemplateSelector: DataTemplateSelector
    {
        public EmptyDataTemplateSelector()
        {
            Checker = new DefaultEmptyTemplateChecker();
        }
        public DataTemplate Empty { get; set; }
        public DataTemplate Use { get; set; }
        public IEmptyTemplateChecker Checker { get; set; }
        public override DataTemplate SelectTemplate(object item, DependencyObject container)
        {
            if (Checker == null)
                return Empty;
            var isEmpty = Checker.IsEmpty(item);
            var dataTemplate = isEmpty ? Empty : Use;
            return dataTemplate;
        }
    }
}