BehaviorGeneric.cs

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// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
using Dreamine.MVVM.Behaviors.Core.Interfaces;
using System.Diagnostics;
using System.Windows;
 
namespace Dreamine.MVVM.Behaviors.Core.Base
{
    public abstract class Behavior<T> : Freezable, IAttachedObject where T : DependencyObject
    {
        public T? AssociatedObject { get; private set; }

        DependencyObject IAttachedObject.AssociatedObject => AssociatedObject!;

        public void Attach(DependencyObject dependencyObject)
        {
            if (dependencyObject is not T typed)
            {
                throw new InvalidOperationException(
                    $"Behavior<{typeof(T).Name}> requires a {typeof(T).Name} " +
                    $"but received {dependencyObject?.GetType().Name ?? "null"}.");
            }
 
            AssociatedObject = typed;
            OnAttached();
        }

        public void Detach()
        {
            OnDetaching();
            AssociatedObject = null;
        }

        protected virtual void OnAttached()
        {           
        }

        protected virtual void OnDetaching()
        {           
        }

        protected override Freezable CreateInstanceCore()
        {
            return (Freezable)Activator.CreateInstance(GetType())!;
        }
    }
}