WPF ICommand 用法

  1 using System;
  2 using System.Collections.Generic;
  3 using System.Linq;
  4 using System.Text;
  5 using System.Windows.Input;
  6 
  7 namespace WpfExample
  8 {
  9     public class RelayCommand : ICommand
 10     {
 11         #region Fields
 12 
 13         /// <summary>
 14         /// Encapsulated the execute action
 15         /// </summary>
 16         private Action<object> execute;
 17 
 18         /// <summary>
 19         /// Encapsulated the representation for the validation of the execute method
 20         /// </summary>
 21         private Predicate<object> canExecute;
 22 
 23         #endregion // Fields
 24 
 25         #region Constructors
 26 
 27         /// <summary>
 28         /// Initializes a new instance of the RelayCommand class
 29         /// Creates a new command that can always execute.
 30         /// </summary>
 31         /// <param name="execute">The execution logic.</param>
 32         public RelayCommand(Action<object> execute)
 33             : this(execute, DefaultCanExecute)
 34         {
 35         }
 36 
 37         /// <summary>
 38         /// Initializes a new instance of the RelayCommand class
 39         /// Creates a new command.
 40         /// </summary>
 41         /// <param name="execute">The execution logic.</param>
 42         /// <param name="canExecute">The execution status logic.</param>
 43         public RelayCommand(Action<object> execute, Predicate<object> canExecute)
 44         {
 45             if (execute == null)
 46             {
 47                 throw new ArgumentNullException("execute");
 48             }
 49 
 50             if (canExecute == null)
 51             {
 52                 throw new ArgumentNullException("canExecute");
 53             }
 54 
 55             this.execute = execute;
 56             this.canExecute = canExecute;
 57         }
 58 
 59         #endregion // Constructors
 60 
 61         #region ICommand Members
 62 
 63         /// <summary>
 64         /// An event to raise when the CanExecute value is changed
 65         /// </summary>
 66         /// <remarks>
 67         /// Any subscription to this event will automatically subscribe to both 
 68         /// the local OnCanExecuteChanged method AND
 69         /// the CommandManager RequerySuggested event
 70         /// </remarks>
 71         public event EventHandler CanExecuteChanged
 72         {
 73             add
 74             {
 75                 CommandManager.RequerySuggested += value;
 76                 this.CanExecuteChangedInternal += value;
 77             }
 78 
 79             remove
 80             {
 81                 CommandManager.RequerySuggested -= value;
 82                 this.CanExecuteChangedInternal -= value;
 83             }
 84         }
 85 
 86         /// <summary>
 87         /// An event to allow the CanExecuteChanged event to be raised manually
 88         /// </summary>
 89         private event EventHandler CanExecuteChangedInternal;
 90 
 91         /// <summary>
 92         /// Defines if command can be executed
 93         /// </summary>
 94         /// <param name="parameter">the parameter that represents the validation method</param>
 95         /// <returns>true if the command can be executed</returns>
 96         public bool CanExecute(object parameter)
 97         {
 98             return this.canExecute != null && this.canExecute(parameter);
 99         }
100 
101         /// <summary>
102         /// Execute the encapsulated command
103         /// </summary>
104         /// <param name="parameter">the parameter that represents the execution method</param>
105         public void Execute(object parameter)
106         {
107             this.execute(parameter);
108         }
109 
110         #endregion // ICommand Members
111 
112         /// <summary>
113         /// Raises the can execute changed.
114         /// </summary>
115         public void OnCanExecuteChanged()
116         {
117             EventHandler handler = this.CanExecuteChangedInternal;
118             if (handler != null)
119             {
120                 //DispatcherHelper.BeginInvokeOnUIThread(() => handler.Invoke(this, EventArgs.Empty));
121                 handler.Invoke(this, EventArgs.Empty);
122             }
123         }
124 
125         /// <summary>
126         /// Destroys this instance.
127         /// </summary>
128         public void Destroy()
129         {
130             this.canExecute = _ => false;
131             this.execute = _ => { return; };
132         }
133 
134         /// <summary>
135         /// Defines if command can be executed (default behaviour)
136         /// </summary>
137         /// <param name="parameter">The parameter.</param>
138         /// <returns>Always true</returns>
139         private static bool DefaultCanExecute(object parameter)
140         {
141             return true;
142         }
143     }
144 }

 1   public ICommand ToggleExecuteCommand { get;set; }//前台绑定的命令
 2         public ICommand HiButtonCommand { get; set; }//前台绑定的命令
 3        
 4         public MainWindowViewModel()
 5         {
 6             HiButtonCommand = new RelayCommand(ShowMessage,CanExecute2);//初始化命令调用的方法
 7             ToggleExecuteCommand = new RelayCommand(ChangeCanExecute);//初始化命令调用的方法
 8         }
 9 
10         private bool CanExecute2(object obj)//调用的方法体函数
11         {
12             return true;
13         }
14 
15         public void ShowMessage(object obj)//调用的方法体函数
16         {
17             MessageBox.Show(obj.ToString());
18         }
19 
20         public void ChangeCanExecute(object obj)//调用的方法体函数
21         {
22             //
23         }