push notification helper library

http://windowsteamblog.com/windows_phone/b/wpdev/archive/2011/01/14/windows-push-notification-server-side-helper-library.aspx
http://create.msdn.com/en-us/education/catalog/article/pnhelp-wp7

main/Libs/PushRecipe_WP7_SL/Source/WindowsPhone.Recipes.Push.Server/ViewModels/RelayCommand.cs

@@ -0,0 +1,69 @@
+using System;
+using System.Diagnostics;
+using System.Windows.Input;
+
+namespace WindowsPhone.Recipes.Push.Server.ViewModels
+{
+    /// <summary>
+    /// A custom implementation of a WPF command, command whose sole purpose is
+    /// to relay its functionality to other objects by invoking delegates.
+    /// The default return value for the CanExecute method is 'true'.
+    /// </summary>
+    public class RelayCommand : ICommand
+    {
+        #region Fields
+
+        private readonly Action<object> _execute;
+        private readonly Predicate<object> _canExecute;        
+
+        #endregion // Fields
+
+        #region Constructors
+
+        /// <summary>
+        /// Creates a new command that can always execute.
+        /// </summary>
+        /// <param name="execute">The execution logic.</param>
+        public RelayCommand(Action<object> execute)
+            : this(execute, null)
+        {
+        }
+
+        /// <summary>
+        /// Creates a new command.
+        /// </summary>
+        /// <param name="execute">The execution logic.</param>
+        /// <param name="canExecute">The execution status logic.</param>
+        public RelayCommand(Action<object> execute, Predicate<object> canExecute)
+        {
+            if (execute == null)
+                throw new ArgumentNullException("execute");
+
+            _execute = execute;
+            _canExecute = canExecute;           
+        }
+
+        #endregion // Constructors
+
+        #region ICommand Members
+
+        [DebuggerStepThrough]
+        public bool CanExecute(object parameter)
+        {
+            return _canExecute == null ? true : _canExecute(parameter);
+        }
+
+        public event EventHandler CanExecuteChanged
+        {
+            add { CommandManager.RequerySuggested += value; }
+            remove { CommandManager.RequerySuggested -= value; }
+        }
+
+        public void Execute(object parameter)
+        {
+            _execute(parameter);
+        }
+
+        #endregion // ICommand Members
+    }
+}