WPF NotifyIcon

--------------
ADD   Added ParentTaskbarIcon attached dependency property which is set for tooltips, popups, and custom balloons.
CHG   Made CloseBalloon public.
CHG   Changed sample, cleaned up commands pattern.


git-svn-id: https://svn.evolvesoftware.ch/repos/evolve.net/WPF/NotifyIcon@93 9f600761-6f11-4665-b6dc-0185e9171623

Source/Sample Project/Commands/CommandBase.cs

@@ -0,0 +1,64 @@
+using System;
+using System.Windows.Input;
+using System.Windows.Markup;
+
+namespace Sample_Project.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 true;
+    }
+  }
+}