Neuerstellung

FSI.BT.Tools/Commands/CommandBase.cs

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+using System;
+using System.ComponentModel;
+using System.Windows;
+using System.Windows.Input;
+using System.Windows.Markup;
+using System.Windows.Media;
+using Hardcodet.Wpf.TaskbarNotification;
+
+namespace FSI.BT.Tools.Commands
+{
+    /// <summary>
+    /// Basic implementation of the <see cref="ICommand"/>
+    /// interface, which is also accessible as a markup
+    /// extension.
+    /// </summary>
+    public abstract class CommandBase<T> : MarkupExtension, ICommand
+        where T : class, ICommand, new()
+    {
+        /// <summary>
+        /// A singleton instance.
+        /// </summary>
+        private static T? command;
+
+        /// <summary>
+        /// Gets a shared command instance.
+        /// </summary>
+        public override object ProvideValue(IServiceProvider serviceProvider)
+        {
+            if (command == null) command = new T();
+            return command;
+        }
+
+        /// <summary>
+        /// Fires when changes occur that affect whether
+        /// or not the command should execute.
+        /// </summary>
+        public event EventHandler CanExecuteChanged
+        {
+            add { CommandManager.RequerySuggested += value; }
+            remove { CommandManager.RequerySuggested -= value; }
+        }
+
+        /// <summary>
+        /// Defines the method to be called when the command is invoked.
+        /// </summary>
+        /// <param name="parameter">Data used by the command.
+        /// If the command does not require data to be passed,
+        /// this object can be set to null.
+        /// </param>
+        public abstract void Execute(object parameter);
+
+        /// <summary>
+        /// Defines the method that determines whether the command
+        /// can execute in its current state.
+        /// </summary>
+        /// <returns>
+        /// This default implementation always returns true.
+        /// </returns>
+        /// <param name="parameter">Data used by the command.  
+        /// If the command does not require data to be passed,
+        /// this object can be set to null.
+        /// </param>
+        public virtual bool CanExecute(object parameter)
+        {
+            return !IsDesignMode;
+        }
+
+
+        public static bool IsDesignMode
+        {
+            get
+            {
+                return (bool)
+                    DependencyPropertyDescriptor.FromProperty(DesignerProperties.IsInDesignModeProperty,
+                        typeof(FrameworkElement))
+                        .Metadata.DefaultValue;
+            }
+        }
+
+
+        /// <summary>
+        /// Resolves the window that owns the TaskbarIcon class.
+        /// </summary>
+        /// <param name="commandParameter"></param>
+        /// <returns>Window</returns>
+        protected Window? GetTaskbarWindow(object commandParameter)
+        {
+            if (IsDesignMode)
+                return null;
+
+            // get the showcase window off the taskbar icon
+            var tb = commandParameter as TaskbarIcon;
+            return tb == null ? null : TryFindParent<Window>(tb);
+        }
+
+        #region TryFindParent helper
+
+        /// <summary>
+        /// Finds a parent of a given item on the visual tree.
+        /// </summary>
+        /// <typeparam name="TParent">The type of the queried item.</typeparam>
+        /// <param name="child">A direct or indirect child of the
+        /// queried item.</param>
+        /// <returns>The first parent item that matches the submitted
+        /// type parameter. If not matching item can be found, a null
+        /// reference is being returned.</returns>
+        public static TParent? TryFindParent<TParent>(DependencyObject child) where TParent : DependencyObject
+        {
+            //get parent item
+            DependencyObject parentObject = GetParentObject(child);
+
+            //we've reached the end of the tree
+            if (parentObject == null) return null;
+
+            //check if the parent matches the type we're looking for
+            if (parentObject is TParent parent)
+            {
+                return parent;
+            }
+
+            //use recursion to proceed with next level
+            return TryFindParent<TParent>(parentObject);
+        }
+
+        /// <summary>
+        /// This method is an alternative to WPF's
+        /// <see cref="VisualTreeHelper.GetParent"/> method, which also
+        /// supports content elements. Keep in mind that for content element,
+        /// this method falls back to the logical tree of the element!
+        /// </summary>
+        /// <param name="child">The item to be processed.</param>
+        /// <returns>The submitted item's parent, if available. Otherwise
+        /// null.</returns>
+        public static DependencyObject? GetParentObject(DependencyObject child)
+        {
+            if (child == null) return null;
+
+            if (child is ContentElement contentElement)
+            {
+                DependencyObject parent = ContentOperations.GetParent(contentElement);
+                if (parent != null) return parent;
+
+                FrameworkContentElement? fce = contentElement as FrameworkContentElement;
+                return fce?.Parent;
+            }
+
+            //if it's not a ContentElement, rely on VisualTreeHelper
+            return VisualTreeHelper.GetParent(child);
+        }
+
+        #endregion
+    }
+}