Document CommandAction and EventAction, and make them consistent

Samples/Stylet.Samples.Hello/ShellView.xaml

@@ -4,7 +4,7 @@
         xmlns:s="http://github.com/canton7/Stylet"
         Height="300" Width="300">
     <StackPanel>
-        <TextBox Text="{Binding Name}"/>
+        <TextBox Text="{Binding Name, UpdateSourceTrigger=PropertyChanged}"/>
         <Button Command="{s:Action SayHello}">Say Hello</Button>
     </StackPanel>
 </Window>

Samples/Stylet.Samples.Hello/ShellViewModel.cs

@@ -9,13 +9,22 @@ namespace Stylet.Samples.Hello
 {
     class ShellViewModel : Screen
     {
-        public string Name { get; set; }
+        private string _name;
+        public string Name
+        {
+            get { return this._name; }
+            set { SetAndNotify(ref this._name, value); this.NotifyOfPropertyChange(() => this.CanSayHello); }
+        }
 
         public ShellViewModel()
         {
             this.DisplayName = "Hello, Stylet";
         }
 
+        public bool CanSayHello
+        {
+            get { return !String.IsNullOrEmpty(this.Name); }
+        }
         public void SayHello()
         {
             MessageBox.Show(String.Format("Hello, {0}", this.Name)); // Don't do this

Stylet/ActionExtension.cs

@@ -30,13 +30,13 @@ namespace Stylet
             var propertyAsDependencyProperty = valueService.TargetProperty as DependencyProperty;
             if (propertyAsDependencyProperty != null && propertyAsDependencyProperty.PropertyType == typeof(ICommand))
             {
-                return new ActionCommand((FrameworkElement)valueService.TargetObject, this.Method);
+                return new CommandAction((FrameworkElement)valueService.TargetObject, this.Method);
             }
 
             var propertyAsEventInfo = valueService.TargetProperty as EventInfo;
             if (propertyAsEventInfo != null)
             {
-                var ec = new EventCommand((FrameworkElement)valueService.TargetObject, propertyAsEventInfo, this.Method);
+                var ec = new EventAction((FrameworkElement)valueService.TargetObject, propertyAsEventInfo, this.Method);
                 return ec.GetDelegate();
             }
                 

Stylet/CommandAction.cs

@@ -13,23 +13,52 @@ using Expressions = System.Linq.Expressions;
 
 namespace Stylet
 {
-    public class ActionCommand : ICommand
+    /// <summary>
+    /// ICommand returned by ActionExtension for binding buttons, etc, to methods on a ViewModel.
+    /// If the method has a parameter, CommandParameter is passed
+    /// </summary>
+    /// <remarks>
+    /// Watches the current View.ActionTarget, and looks for a method with the given name, calling it when the ICommand is called.
+    /// If a bool property with name Get(methodName) exists, it will be observed and used to enable/disable the ICommand.
+    /// </remarks>
+    public class CommandAction : ICommand
     {
+        /// <summary>
+        /// View to grab the View.ActionTarget from
+        /// </summary>
         private FrameworkElement subject;
+
+        /// <summary>
+        /// Method name. E.g. if someone's gone Buttom Command="{s:Action MyMethod}", this is MyMethod.
+        /// </summary>
         private string methodName;
+
+        /// <summary>
+        /// Generated accessor to grab the value of the guard property, or null if there is none
+        /// </summary>
         private Func<bool> guardPropertyGetter;
+
+        /// <summary>
+        /// MethodInfo for the method to call. This has to exist, or we throw a wobbly
+        /// </summary>
         private MethodInfo targetMethodInfo;
 
         private object target;
 
-        public ActionCommand(FrameworkElement subject, string methodName)
+        /// <summary>
+        /// Create a new ActionCommand 
+        /// </summary>
+        /// <param name="subject">View to grab the View.ActionTarget from</param>
+        /// <param name="methodName">Method name. the MyMethod in Buttom Command="{s:Action MyMethod}".</param>
+        public CommandAction(FrameworkElement subject, string methodName)
         {
             this.subject = subject;
             this.methodName = methodName;
 
-            this.UpdateGuardHandler();
+            this.UpdateGuardAndMethod();
 
-            DependencyPropertyDescriptor.FromProperty(View.ActionTargetProperty, typeof(View)).AddValueChanged(this.subject, (o, e) => this.UpdateGuardHandler());
+            // Observe the View.ActionTarget for changes, and re-bind the guard property and MethodInfo if it changes
+            DependencyPropertyDescriptor.FromProperty(View.ActionTargetProperty, typeof(View)).AddValueChanged(this.subject, (o, e) => this.UpdateGuardAndMethod());
         }
 
         private string GuardName
@@ -37,7 +66,7 @@ namespace Stylet
             get { return "Can" + this.methodName; }
         }
 
-        private void UpdateGuardHandler()
+        private void UpdateGuardAndMethod()
         {
             var newTarget = View.GetActionTarget(this.subject);
             MethodInfo targetMethodInfo = null;
@@ -50,9 +79,9 @@ namespace Stylet
                 var guardPropertyInfo = newTargetType.GetProperty(this.GuardName);
                 if (guardPropertyInfo != null && guardPropertyInfo.PropertyType == typeof(bool))
                 {
-                    var param = Expressions.Expression.Parameter(typeof(bool), "returnValue");
+                    var targetExpression = Expressions.Expression.Constant(newTarget);
-                    var propertyAccess = Expressions.Expression.Property(param, guardPropertyInfo);
+                    var propertyAccess = Expressions.Expression.Property(targetExpression, guardPropertyInfo);
-                    this.guardPropertyGetter = Expressions.Expression.Lambda<Func<bool>>(propertyAccess, param).Compile();
+                    this.guardPropertyGetter = Expressions.Expression.Lambda<Func<bool>>(propertyAccess).Compile();
                 }
 
                 targetMethodInfo = newTargetType.GetMethod(this.methodName);

Stylet/EventAction.cs

@@ -8,36 +8,55 @@ using System.Windows;
 
 namespace Stylet
 {
-    public class EventCommand
+    /// <summary>
+    /// Created by ActionExtension, this can return a delegate suitable adding binding to an event, and can call a method on the View.ActionTarget
+    /// </summary>
+    public class EventAction
     {
+        /// <summary>
+        /// View whose View.ActionTarget we watch
+        /// </summary>
         private FrameworkElement subject;
+
+        /// <summary>
+        /// Property on the WPF element we're returning a delegate for
+        /// </summary>
         private EventInfo targetProperty;
+
+        /// <summary>
+        /// The MyMethod in {s:Action MyMethod}, this is what we call when the event's fired
+        /// </summary>
         private string methodName;
 
-        public EventCommand(FrameworkElement subject, EventInfo targetProperty, string methodName)
+        /// <summary>
+        /// Create a new EventAction
+        /// </summary>
+        /// <param name="subject">View whose View.ActionTarget we watch</param>
+        /// <param name="targetProperty">Property on the WPF element we're returning a delegate for</param>
+        /// <param name="methodName">The MyMethod in {s:Action MyMethod}, this is what we call when the event's fired</param>
+        public EventAction(FrameworkElement subject, EventInfo targetProperty, string methodName)
         {
             this.subject = subject;
             this.targetProperty = targetProperty;
             this.methodName = methodName;
         }
 
+        /// <summary>
+        /// Return a delegate which can be added to the targetProperty
+        /// </summary>
         public Delegate GetDelegate()
         {
-            Delegate del = null;
-
             var methodInfo = this.GetType().GetMethod("InvokeCommand", BindingFlags.NonPublic | BindingFlags.Instance);
 
             var parameterType = this.targetProperty.EventHandlerType;
-            del = Delegate.CreateDelegate(parameterType, this, methodInfo);
+            return Delegate.CreateDelegate(parameterType, this, methodInfo);
-
-            return del;
         }
 
         private void InvokeCommand(object sender, RoutedEventArgs e)
         {
             var target = View.GetActionTarget(this.subject);
             if (target == null)
-                throw new Exception("Target not set");
+                return;
 
             var methodInfo = target.GetType().GetMethod(this.methodName);
             if (methodInfo == null)