From 15b87f46850c6566f7846b10700f46ab724027dc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=AD=B1=E5=82=91?= <840465812@qq.com>
Date: Fri, 2 Aug 2019 14:26:44 +0800
Subject: [PATCH] Add MVVM Base

Add DelegateCommand
Add ViewModelBase
---
 MVVM/DelegateCommand.cs | 297 ++++++++++++++++++++++++++++++++++++++++
 MVVM/ViewModelBase.cs   |  46 +++++++
 2 files changed, 343 insertions(+)
 create mode 100644 MVVM/DelegateCommand.cs
 create mode 100644 MVVM/ViewModelBase.cs

diff --git a/MVVM/DelegateCommand.cs b/MVVM/DelegateCommand.cs
new file mode 100644
index 0000000..3d14b55
--- /dev/null
+++ b/MVVM/DelegateCommand.cs
@@ -0,0 +1,297 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Windows;
+using System.Windows.Input;
+using System.Windows.Threading;
+
+namespace Command
+{
+
+    /// <summary>
+    /// Provides an <see cref="ICommand"/> implementation which relays the Execute and CanExecute
+    /// method to the specified delegates.
+    /// </summary>
+    public class DelegateCommand : ICommand
+    {
+        #region Static disabled command
+
+        /// <summary>
+        /// A <see cref="DelegateCommand"/> instance that does nothing and can never be executed.
+        /// </summary>
+        public static readonly DelegateCommand Disabled = new DelegateCommand(() => { }) { IsEnabled = false };
+
+        #endregion Static disabled command
+
+        #region Private data
+
+        private readonly Action<object> execute;
+        private readonly Func<object, bool> canExecute;
+        private List<WeakReference> weakHandlers;
+        private bool? isEnabled;
+        private bool raiseCanExecuteChangedPending;
+
+        #endregion Private data
+
+        #region Constructors
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DelegateCommand"/> class.
+        /// </summary>
+        /// <param name="execute">Delegate to execute when Execute is called on the command.</param>
+        /// <exception cref="ArgumentNullException">The execute argument must not be null.</exception>
+        public DelegateCommand(Action execute)
+            : this(execute != null ? p => execute() : (Action<object>)null, (Func<object, bool>)null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DelegateCommand"/> class.
+        /// </summary>
+        /// <param name="execute">Delegate to execute when Execute is called on the command.</param>
+        /// <param name="canExecute">Delegate to execute when CanExecute is called on the command.</param>
+        /// <exception cref="ArgumentNullException">The execute argument must not be null.</exception>
+        public DelegateCommand(Action execute, Func<bool> canExecute)
+            : this(execute != null ? p => execute() : (Action<object>)null, canExecute != null ? p => canExecute() : (Func<object, bool>)null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DelegateCommand"/> class.
+        /// </summary>
+        /// <param name="execute">Delegate to execute when Execute is called on the command.</param>
+        /// <param name="canExecute">Delegate to execute when CanExecute is called on the command.</param>
+        /// <exception cref="ArgumentNullException">The execute argument must not be null.</exception>
+        public DelegateCommand(Action execute, Func<object, bool> canExecute)
+            : this(execute != null ? p => execute() : (Action<object>)null, canExecute)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DelegateCommand"/> class.
+        /// </summary>
+        /// <param name="execute">Delegate to execute when Execute is called on the command.</param>
+        /// <exception cref="ArgumentNullException">The execute argument must not be null.</exception>
+        public DelegateCommand(Action<object> execute)
+            : this(execute, (Func<object, bool>)null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DelegateCommand"/> class.
+        /// </summary>
+        /// <param name="execute">Delegate to execute when Execute is called on the command.</param>
+        /// <param name="canExecute">Delegate to execute when CanExecute is called on the command.</param>
+        /// <exception cref="ArgumentNullException">The execute argument must not be null.</exception>
+        public DelegateCommand(Action<object> execute, Func<bool> canExecute)
+            : this(execute, canExecute != null ? p => canExecute() : (Func<object, bool>)null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="DelegateCommand"/> class.
+        /// </summary>
+        /// <param name="execute">Delegate to execute when Execute is called on the command.</param>
+        /// <param name="canExecute">Delegate to execute when CanExecute is called on the command.</param>
+        /// <exception cref="ArgumentNullException">The execute argument must not be null.</exception>
+        public DelegateCommand(Action<object> execute, Func<object, bool> canExecute)
+        {
+            if (execute == null)
+                throw new ArgumentNullException(nameof(execute));
+
+            this.execute = execute;
+            this.canExecute = canExecute;
+        }
+
+        #endregion Constructors
+
+        #region CanExecuteChanged event
+
+        /// <summary>
+        /// Occurs when changes occur that affect whether or not the command should execute.
+        /// </summary>
+        public event EventHandler CanExecuteChanged
+        {
+            add
+            {
+                if (weakHandlers == null)
+                {
+                    weakHandlers = new List<WeakReference>(new[] { new WeakReference(value) });
+                }
+                else
+                {
+                    weakHandlers.Add(new WeakReference(value));
+                }
+            }
+            remove
+            {
+                if (weakHandlers == null) return;
+
+                for (int i = weakHandlers.Count - 1; i >= 0; i--)
+                {
+                    WeakReference weakReference = weakHandlers[i];
+                    EventHandler handler = weakReference.Target as EventHandler;
+                    if (handler == null || handler == value)
+                    {
+                        weakHandlers.RemoveAt(i);
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Raises the <see cref="E:CanExecuteChanged"/> event.
+        /// </summary>
+        [DebuggerStepThrough]
+        public void RaiseCanExecuteChanged() => OnCanExecuteChanged();
+
+        /// <summary>
+        /// Raises the <see cref="E:CanExecuteChanged"/> event after all other processing has
+        /// finished. Multiple calls to this function before the asynchronous action has been
+        /// started are ignored.
+        /// </summary>
+        [DebuggerStepThrough]
+        public void RaiseCanExecuteChangedAsync()
+        {
+            if (!raiseCanExecuteChangedPending)
+            {
+                // Don't do anything if not on the UI thread. The dispatcher event will never be
+                // fired there and probably there's nobody interested in changed properties anyway
+                // on that thread.
+                if (Dispatcher.CurrentDispatcher == Application.Current.Dispatcher)
+                {
+                    Dispatcher.CurrentDispatcher.BeginInvoke((Action)OnCanExecuteChanged, DispatcherPriority.Loaded);
+                    raiseCanExecuteChangedPending = true;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Raises the <see cref="E:CanExecuteChanged"/> event.
+        /// </summary>
+        [DebuggerStepThrough]
+        protected virtual void OnCanExecuteChanged()
+        {
+            raiseCanExecuteChangedPending = false;
+            PurgeWeakHandlers();
+            if (weakHandlers == null) return;
+
+            WeakReference[] handlers = weakHandlers.ToArray();
+            foreach (WeakReference reference in handlers)
+            {
+                EventHandler handler = reference.Target as EventHandler;
+                handler?.Invoke(this, EventArgs.Empty);
+            }
+        }
+
+        [DebuggerStepThrough]
+        private void PurgeWeakHandlers()
+        {
+            if (weakHandlers == null) return;
+
+            for (int i = weakHandlers.Count - 1; i >= 0; i--)
+            {
+                if (!weakHandlers[i].IsAlive)
+                {
+                    weakHandlers.RemoveAt(i);
+                }
+            }
+
+            if (weakHandlers.Count == 0)
+                weakHandlers = null;
+        }
+
+        #endregion CanExecuteChanged event
+
+        #region ICommand methods
+
+        /// <summary>
+        /// Defines the method that determines whether the command can execute in its current state.
+        /// </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>
+        /// <returns>true if this command can be executed; otherwise, false.</returns>
+        [DebuggerStepThrough]
+        public bool CanExecute(object parameter) => isEnabled ?? canExecute?.Invoke(parameter) ?? true;
+
+        /// <summary>
+        /// Convenience method that invokes CanExecute without parameters.
+        /// </summary>
+        /// <returns>true if this command can be executed; otherwise, false.</returns>
+        [DebuggerStepThrough]
+        public bool CanExecute() => CanExecute(null);
+
+        /// <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>
+        /// <exception cref="InvalidOperationException">The <see cref="CanExecute(object)"/> method returns false.</exception>
+        [DebuggerStepThrough]
+        public void Execute(object parameter)
+        {
+            if (!CanExecute(parameter))
+            {
+                throw new InvalidOperationException("The command cannot be executed because CanExecute returned false.");
+            }
+            execute(parameter);
+        }
+
+        /// <summary>
+        /// Convenience method that invokes the command without parameters.
+        /// </summary>
+        /// <exception cref="InvalidOperationException">The <see cref="CanExecute(object)"/> method returns false.</exception>
+        [DebuggerStepThrough]
+        public void Execute() => Execute(null);
+
+        /// <summary>
+        /// Invokes the command if the <see cref="CanExecute(object)"/> method returns true.
+        /// </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>
+        /// <returns>true if this command was executed; otherwise, false.</returns>
+        public bool TryExecute(object parameter)
+        {
+            if (CanExecute(parameter))
+            {
+                Execute(parameter);
+                return true;
+            }
+            return false;
+        }
+
+        /// <summary>
+        /// Convenience method that invokes the command without parameters if the
+        /// <see cref="CanExecute(object)"/> method returns true.
+        /// </summary>
+        /// <returns>true if this command was executed; otherwise, false.</returns>
+        [DebuggerStepThrough]
+        public bool TryExecute() => TryExecute(null);
+
+        #endregion ICommand methods
+
+        #region Enabled state
+
+        /// <summary>
+        /// Gets or sets a value indicating whether the current DelegateCommand is enabled. If this
+        /// value is not null, it takes precedence over the canExecute function was passed in the
+        /// constructor. If no function was passed and this value is null the command is enabled.
+        /// </summary>
+        public bool? IsEnabled
+        {
+            [DebuggerStepThrough]
+            get
+            {
+                return isEnabled;
+            }
+            [DebuggerStepThrough]
+            set
+            {
+                if (value != isEnabled)
+                {
+                    isEnabled = value;
+                    RaiseCanExecuteChanged();
+                }
+            }
+        }
+
+        #endregion Enabled state
+    }
+}
\ No newline at end of file
diff --git a/MVVM/ViewModelBase.cs b/MVVM/ViewModelBase.cs
new file mode 100644
index 0000000..42d3844
--- /dev/null
+++ b/MVVM/ViewModelBase.cs
@@ -0,0 +1,46 @@
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+
+namespace ViewModel
+{
+    public abstract class ViewModelBase : INotifyPropertyChanged
+    {
+        /// <summary>
+        /// Multicast event for property change notifications.
+        /// </summary>
+        public event PropertyChangedEventHandler PropertyChanged;
+
+        /// <summary>
+        /// Checks if a property already matches a desired value.  Sets the property and
+        /// notifies listeners only when necessary.
+        /// </summary>
+        /// <typeparam name="T">Type of the property.</typeparam>
+        /// <param name="storage">Reference to a property with both getter and setter.</param>
+        /// <param name="value">Desired value for the property.</param>
+        /// <param name="propertyName">Name of the property used to notify listeners.This
+        /// value is optional and can be provided automatically when invoked from compilers that
+        /// support CallerMemberName.</param>
+        /// <returns>True if the value was changed, false if the existing value matched the
+        /// desired value.</returns>
+        protected virtual bool SetProperty<T>(ref T storage, T value, [CallerMemberName] string propertyName = null)
+        {
+            if (Equals(storage, value))
+                return false;
+            storage = value;
+            // Log.DebugFormat("{0}.{1} = {2}", this.GetType().Name, propertyName, storage);
+            OnPropertyChanged(propertyName);
+            return true;
+        }
+
+        /// <summary>
+        /// Notifies listeners that a property value has changed.
+        /// </summary>
+        /// <param name="propertyName">Name of the property used to notify listeners.  This
+        /// value is optional and can be provided automatically when invoked from compilers
+        /// that support <see cref="CallerMemberNameAttribute"/>.</param>
+        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
+        {
+            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+        }
+    }
+}
\ No newline at end of file