WPF 一个MVVM的简单例子

如下图是系统的结构图：这个示例是模仿计算器的MVVM模式的精简版，非常简单。

这篇文章就开门见山了，有关MVVM的理论部分，请参考MVVM设计模式

1、App中的代码：

public  App()
{
    CalculatorView view = new  CalculatorView();
    view.DataContext = new  CalculatorViewModel();
    view.Show();
}

2、Model层中CauculatorModel的代码

class  CauculatorModel
{
     public  string  FirstOperand { get ; set ; }
     public  string  SecondOperand { get ; set ; }
     public  string  Operation { get ; set ; }
     public  string  Result { get ; set ; }
}

3、Command

public  class  DeletgateCommand:ICommand
 {
     private  readonly  Action _executeMethod = null ;
     private  readonly  Func bool > _canExecuteMethod = null ;

     public  DeletgateCommand(Action executeMethod)
         : this (executeMethod, null )
     { }

     public  DeletgateCommand(Action executeMethod, Func bool > canExecuteMethod)
     {
         if  (executeMethod == null )
             throw  new  ArgumentNullException( "executeMetnod" );
         _executeMethod = executeMethod;
         _canExecuteMethod = canExecuteMethod;
     }

     #region ICommand 成员
     ///
     ///  Method to determine if the command can be executed
     ///
     public  bool  CanExecute(T parameter)
     {
         if  (_canExecuteMethod != null )
         {
             return  _canExecuteMethod(parameter);
         }
         return  true ;

     }

     ///
     ///  Execution of the command
     ///
     public  void  Execute(T parameter)
     {
         if  (_executeMethod != null )
         {
             _executeMethod(parameter);
         }
     }

     #endregion


     event  EventHandler ICommand.CanExecuteChanged
     {
         add { CommandManager.RequerySuggested += value; }
         remove { CommandManager.RequerySuggested -= value; }
     }

     #region ICommand 成员

     public  bool  CanExecute( object  parameter)
     {
         if  (parameter == null  && typeof (T).IsValueType)
         {
             return  (_canExecuteMethod == null );

         }

         return  CanExecute((T)parameter);
     }

     public  void  Execute( object  parameter)
     {
         Execute((T)parameter);
     }

     #endregion
 }

 

4、ViewModwl层，为了简化，此处Add方法采用硬编码的形式

public  class  CalculatorViewModel
 {
     CauculatorModel calculatorModel;
     private  DeletgateCommand< string > addCommand;


     public  CalculatorViewModel()
     {
         calculatorModel = new  CauculatorModel();
     }

     #region Public Properties
     public  string  FirstOperand
     {
         get  {  return  calculatorModel.FirstOperand;  }
         set  { calculatorModel.FirstOperand = value;  }
     }
     public  string  SecondOperand
     {
         get  { return  calculatorModel.SecondOperand; }
         set  { calculatorModel.SecondOperand = value; }
     }
     public  string  Operation
     {
         get  { return  calculatorModel.Operation; }
         set  { calculatorModel.Operation = value; }
     }
     public  string  Result
     {
         get  { return  calculatorModel.Result; }
         set  { calculatorModel.Result = value; }
     }
     #endregion

     public  ICommand AddCommand
     {
         get
         {
             if  (addCommand == null )
             {
                 addCommand = new  DeletgateCommand< string >(Add, CanAdd);
             }
             return  addCommand;

         }
     }

     public   void  Add( string  x)
     {
         FirstOperand = x;
         SecondOperand = x;
         Result = ( double .Parse(FirstOperand) + double .Parse(SecondOperand)).ToString();
         Operation = "+" ;
         MessageBox.Show( FirstOperand+ Operation +SecondOperand + "="  + Result);
     }

     private  static  bool  CanAdd( string  num)
     {
         return  true ;
     }
 }

 

ViewModelBase中的代码：

public  abstract  class  ViewModelBase : INotifyPropertyChanged
 {
     public  event  PropertyChangedEventHandler PropertyChanged;

     protected  void  OnPropertyChanged( string  propertyName)
     {
         PropertyChangedEventHandler handler = PropertyChanged;

         if  (handler != null )
         {
             handler( this , new  PropertyChangedEventArgs(propertyName));
         }
     }

 }

 5、View层

       "23"  Margin= "12,63,0,0"  Name= "textBox1"  VerticalAlignment= "Top"  HorizontalAlignment= "Left"   Width= "120"  />
       "12,25,95,0"  Name= "label2"  Height= "32"  VerticalAlignment= "Top" >请输入x的值！ x+x=?
       "23"  Command= "{Binding AddCommand}"
               CommandParameter= "{Binding ElementName=textBox1,Path=Text}"    HorizontalAlignment= "Left"  Margin= "12,102,0,0"  Name= "button1"  VerticalAlignment= "Top"  Width= "75" >
           确定

 CommandParameter里传递的是一个参数，当然可以传递多个参数。

6、效果图：

参考资料：MVVM的一个Example

 

本文转自Work Hard Work Smart博客园博客，原文链接：http://www.cnblogs.com/linlf03/archive/2011/09/11/2173833.html，如需转载请自行联系原作者