❔ PopupModal dialog not fadeout or fadein

using Kasir.Commons.Commands;
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;

namespace Kasir.Utils.Controls
{
    internal class PopupModal : ContentControl
    {

        event EventHandler PopupClosed;
        public ICommand DismissCommand {  get; }

        static PopupModal()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(PopupModal), new FrameworkPropertyMetadata(typeof(PopupModal)));
        }

        public PopupModal()
        {
            DismissCommand = new RelayCommand(Dismiss);
        }

        private void Dismiss(object view) => IsOpen = false;

        public bool IsOpen
        {
            get { return (bool)GetValue(IsOpenProperty); }
            set { 
                SetValue(IsOpenProperty, value); 
                if (!value) PopupClosed?.Invoke(this, EventArgs.Empty);
            }
        }

        public static readonly DependencyProperty IsOpenProperty =
            DependencyProperty.Register("IsOpen", typeof(bool), typeof(PopupModal), new PropertyMetadata(false));

        public string Header
        {
            get { return (string)GetValue(HeaderProperty); }
            set { SetValue(HeaderProperty, value); }
        }
        public static readonly DependencyProperty HeaderProperty =
            DependencyProperty.Register("Header", typeof(string), typeof(PopupModal), new PropertyMetadata("Message Popup"));
    }
}

using Kasir.Commons.Commands;
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;

namespace Kasir.Utils.Controls
{
    internal class PopupModal : ContentControl
    {

        event EventHandler PopupClosed;
        public ICommand DismissCommand {  get; }

        static PopupModal()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(PopupModal), new FrameworkPropertyMetadata(typeof(PopupModal)));
        }

        public PopupModal()
        {
            DismissCommand = new RelayCommand(Dismiss);
        }

        private void Dismiss(object view) => IsOpen = false;

        public bool IsOpen
        {
            get { return (bool)GetValue(IsOpenProperty); }
            set { 
                SetValue(IsOpenProperty, value); 
                if (!value) PopupClosed?.Invoke(this, EventArgs.Empty);
            }
        }

        public static readonly DependencyProperty IsOpenProperty =
            DependencyProperty.Register("IsOpen", typeof(bool), typeof(PopupModal), new PropertyMetadata(false));

        public string Header
        {
            get { return (string)GetValue(HeaderProperty); }
            set { SetValue(HeaderProperty, value); }
        }
        public static readonly DependencyProperty HeaderProperty =
            DependencyProperty.Register("Header", typeof(string), typeof(PopupModal), new PropertyMetadata("Message Popup"));
    }
}