OrderedItem.cs

using System;
using System.Threading.Tasks;
using System.Windows.Input;
 
namespace LegalLab.Models.Items
{
    public abstract class OrderedItem : Model
    {
        private readonly IProperty items;
 
        private readonly Command moveUp;
        private readonly Command moveDown;
 
        public OrderedItem(IProperty Items)
            : base()
        {
            this.items = Items;
 
            this.moveUp = new Command(this.CanExecuteMoveUp, this.ExecuteMoveUp);
            this.moveDown = new Command(this.CanExecuteMoveDown, this.ExecuteMoveDown);
        }
 
        public ICommand MoveUp => this.moveUp;
 
        public ICommand MoveDown => this.moveDown;
 
        public bool CanExecuteMoveUp()
        {
            if (this.items.UntypedValue is Array A)
                return Array.IndexOf(A, this) > 0;
            else
                return false;
        }
 
        public Task ExecuteMoveUp()
        {
            if (this.items.UntypedValue is not Array Items)
                return Task.CompletedTask;
 
            Items = (Array)Items.Clone();
 
            int i = Array.IndexOf(Items, this);
            if (i <= 0)
                return Task.CompletedTask;
 
            object Item1 = Items.GetValue(i - 1);
            object Item2 = Items.GetValue(i);
 
            Items.SetValue(Item2, i - 1);
            Items.SetValue(Item1, i);
 
            this.items.UntypedValue = Items;
 
            return Task.CompletedTask;
        }
 
        public bool CanExecuteMoveDown()
        {
            if (this.items.UntypedValue is Array A)
                return Array.IndexOf(A, this) < A.Length - 1;
            else
                return false;
        }
 
        public Task ExecuteMoveDown()
        {
            if (this.items.UntypedValue is not Array Items)
                return Task.CompletedTask;
 
            Items = (Array)Items.Clone();
 
            int i = Array.IndexOf(Items, this);
            if (i < 0 || i >= Items.Length - 1)
                return Task.CompletedTask;
 
            object Item1 = Items.GetValue(i + 1);
            object Item2 = Items.GetValue(i);
 
            Items.SetValue(Item2, i + 1);
            Items.SetValue(Item1, i);
 
            this.items.UntypedValue = Items;
 
            return Task.CompletedTask;
        }
    }
}