Moves ViewModelBase and RelayCommand to new project, Infrastructure

Author: Declan Taylor

source/Demos/SuggestBoxTestLib/ViewModels/Base/ViewModelBase.cs

@@ -0,0 +1,7 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+	  <TargetFrameworks>net451;netcoreapp3.0</TargetFrameworks>
+  </PropertyGroup>
+
+</Project>

source/Infrastructure/Infrastructure.csproj

@@ -1,9 +1,9 @@
-namespace SuggestBoxTestLib.ViewModels.Base
-{
-	using System;
-	using System.Diagnostics;
-	using System.Windows.Input;
+using System;
+using System.Diagnostics;
+using System.Windows.Input;
 
+namespace Infrastructure
+{
 	/// <summary>
 	/// A command whose sole purpose is to
 	/// relay its functionality to other
@@ -13,7 +13,7 @@
 	///
 	/// Source: http://www.codeproject.com/Articles/31837/Creating-an-Internationalized-Wizard-in-WPF
 	/// </summary>
-	internal class RelayCommand<T> : ICommand
+   public class RelayCommand<T> : ICommand
 	{
 		#region Fields
 
@@ -51,24 +51,11 @@ public RelayCommand(Action<T> execute, Predicate<T> canExecute)
 
 		#region events
 
-		/// <summary>
-		/// Eventhandler to re-evaluate whether this command can execute or not
-		/// </summary>
-		public event EventHandler CanExecuteChanged
-		{
-			add
-			{
-				if (this.mCanExecute != null)
-					CommandManager.RequerySuggested += value;
-			}
-
-			remove
-			{
-				if (this.mCanExecute != null)
-					CommandManager.RequerySuggested -= value;
-			}
-		}
-
+      /// <summary>
+      /// Eventhandler to re-evaluate whether this command can execute or not
+      /// </summary>
+      public event EventHandler CanExecuteChanged;
+	
 		#endregion events
 
 		#region methods
@@ -80,10 +67,16 @@ public event EventHandler CanExecuteChanged
 		/// <returns></returns>
 		[DebuggerStepThrough]
 		public bool CanExecute(object parameter)
-		{
-			return this.mCanExecute == null ? true : this.mCanExecute((T)parameter);
+      {
+         return this.mCanExecute == null || this.mCanExecute((T)parameter);
 		}
 
+
+      public void RaiseCanExecute()
+      {
+         CanExecuteChanged?.Invoke(this, new EventArgs());
+      }
+
 		/// <summary>
 		/// Execute the command method managed in this class.
 		/// </summary>
@@ -150,23 +143,11 @@ public RelayCommand(Action execute, Func<bool> canExecute)
 
 		#region Events
 
-		/// <summary>
-		/// Eventhandler to re-evaluate whether this command can execute or not
-		/// </summary>
-		public event EventHandler CanExecuteChanged
-		{
-			add
-			{
-				if (this.mCanExecute != null)
-					CommandManager.RequerySuggested += value;
-			}
-
-			remove
-			{
-				if (this.mCanExecute != null)
-					CommandManager.RequerySuggested -= value;
-			}
-		}
+      /// <summary>
+      /// Eventhandler to re-evaluate whether this command can execute or not
+      /// </summary>
+      public event EventHandler CanExecuteChanged;
+
 
 		#endregion Events
 

source/Demos/SuggestBoxTestLib/ViewModels/Base/RelayCommand.cs renamed to source/Infrastructure/RelayCommand.cs

@@ -0,0 +1,55 @@
+using System;
+using System.ComponentModel;
+using System.Linq.Expressions;
+using System.Runtime.CompilerServices;
+
+namespace Infrastructure
+{
+   /// <summary>
+	/// Implements a base class for all viewmodel classes
+	/// that implements <seealso cref="INotifyPropertyChanged"/> interface for binding.
+	/// </summary>
+	public class ViewModelBase : INotifyPropertyChanged
+   {
+      /// <summary>
+      /// Standard implementation of <seealso cref="INotifyPropertyChanged"/>.
+      /// </summary>
+      public event PropertyChangedEventHandler PropertyChanged;
+
+      /// <summary>
+      /// Tell bound controls (via WPF binding) to refresh their display.
+      ///
+      /// Sample call: this.NotifyPropertyChanged(() => this.IsSelected);
+      /// where 'this' is derived from <seealso cref="ViewModelBase"/>
+      /// and IsSelected is a property.
+      /// </summary>
+      /// <typeparam name="TProperty"></typeparam>
+      /// <param name="property"></param>
+      public void NotifyPropertyChanged<TProperty>(Expression<Func<TProperty>> property)
+      {
+         var lambda = (LambdaExpression)property;
+         MemberExpression memberExpression;
+
+         if (lambda.Body is UnaryExpression unaryExpression)
+         {
+            memberExpression = (MemberExpression)unaryExpression.Operand;
+         }
+         else
+         {
+            memberExpression = (MemberExpression)lambda.Body;
+         }
+
+         this.NotifyPropertyChanged(memberExpression.Member.Name);
+      }
+
+      /// <summary>
+      /// Tell bound controls (via WPF binding) to refresh their display.
+      /// Standard implementation through <seealso cref="INotifyPropertyChanged"/>.
+      /// </summary>
+      /// <param name="propertyName"></param>
+      protected virtual void NotifyPropertyChanged([CallerMemberName] string propertyName = null)
+      {
+         PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+      }
+   }
+}