WPF 一个MVVM的简单例子

Posted on 2011-09-11 23:24 work hard work smart 阅读(23494) 评论(14) 编辑收藏举报

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>