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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<T>:ICommand 
  { 
      private readonly Action<T> _executeMethod = null; 
      private readonly Func<T,bool> _canExecuteMethod = null; 
      public DeletgateCommand(Action<T> executeMethod) 
          : this(executeMethod, null) 
      { } 
      public DeletgateCommand(Action<T> executeMethod, Func<T,bool> canExecuteMethod)   
      { 
          if (executeMethod == null) 
              throw new ArgumentNullException("executeMetnod"); 
          _executeMethod = executeMethod; 
          _canExecuteMethod = canExecuteMethod; 
      } 
      #region ICommand 成员 
      /// <summary> 
      ///  Method to determine if the command can be executed 
      /// </summary> 
      public bool CanExecute(T parameter) 
      { 
          if (_canExecuteMethod != null) 
          { 
              return _canExecuteMethod(parameter); 
          } 
          return true; 
      } 
      /// <summary> 
      ///  Execution of the command 
      /// </summary> 
      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

 <Grid>    
        <TextBox  Height="23" Margin="12,63,0,0" Name="textBox1" VerticalAlignment="Top" HorizontalAlignment="Left"  Width="120" /> 
        <Label Margin="12,25,95,0" Name="label2" Height="32" VerticalAlignment="Top">请输入x的值！ x+x=? </Label> 
        <Button Height="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</Button> 
    </Grid> 

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

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