WPF MVVMパターン - コントロールのバインディングが機能しない

Question

WPF-MVVMパターンを初めて使用しています。私は2つの数字の加算を実行する小さなアプリケーションを書いています。 2つの数字は、ボタンがクリックされたときに追加が行われる間にユーザーによって入力されます。

問題はResultが3番目のテキストボックスにバインドしていないことです。続き

は私のコード（あなたは追加の問題を発見した場合MVVMに新しいもの、私に知らせてください）です。

のAppクラス - スタートアップ

public partial class App : Application 
{ 
     protected override void OnStartup(StartupEventArgs e) 
     { 
      base.OnStartup(e); 
      MVVM_Math_Calc.Views.Calculator calc = new Views.Calculator(); 
      MVVM_Math_Calc.ViewModels.CalculatorViewModel context = new ViewModels.CalculatorViewModel(); 
      calc.DataContext = context; 
      calc.Show(); 
     } 
    } 

ビュー

<Window x:Class="MVVM_Math_Calc.Views.CalculatorWindow" 
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     Title="Calculator" Height="200" Width="525"> 

    <Grid> 
     <Grid.ColumnDefinitions> 
      <ColumnDefinition Width="1*" /> 
      <ColumnDefinition Width="1*" /> 
      <ColumnDefinition Width="1*" /> 
     </Grid.ColumnDefinitions> 
     <Grid.RowDefinitions> 
      <RowDefinition Height="1*" /> 
      <RowDefinition Height="1*" /> 
      <RowDefinition Height="1*" /> 
     </Grid.RowDefinitions>  
     <Label Content="Number 1" Grid.Column="0" Grid.Row="0" Foreground="Blue" /> 
     <Label Content="Number 1" Grid.Column="1" Grid.Row="0" Foreground="Blue" /> 
     <Label Content="Result"  Grid.Column="2" Grid.Row="0" Foreground="Blue" />  
     <TextBox Name="Num1"  Text="{Binding Number1}" Grid.Column="0" Grid.Row="1" BorderBrush="Gray" /> 
     <TextBox Name="Num2"  Text="{Binding Number2}" Grid.Column="1" Grid.Row="1" BorderBrush="Gray" /> 
     <TextBox Name="Answer"  Text="{Binding Result}"  Grid.Column="2" Grid.Row="1" BorderBrush="Gray" />  
     <Button Content="Addition" Command="{Binding Path=AddNumbersCommand}"  Grid.Column="0" Grid.Row="2" /> 
    </Grid> 
</Window> 

CalculatorViewModel

public class CalculatorViewModel : ViewModelBase 
{ 
     private CalculatorModel calculatorModel; 
     private ICommand  additionCommand; 

     public CalculatorViewModel() 
     { 
      this.CalculatorModel = new CalculatorModel (20, 10); 
     } 

     public CalculatorModel CalculatorModel 
     { 
      get 
      { return calculatorModel; } 
      set 
      { calculatorModel = value; } 
     } 

     public int Result 
     { 
      get { return this.CalculatorModel.Result; } 
      set { this.CalculatorModel.Result = value; } 
     } 

     public int Number1 
     { 
      get { return this.CalculatorModel.Number1; } 
      set { this.CalculatorModel.Number1 = value; } 
     } 

     public int Number2 
     { 
      get { return this.CalculatorModel.Number2; } 
      set { this.CalculatorModel.Number2 = value; } 
     } 

     public ICommand AddNumbersCommand 
     { 
      get 
      { 
       if (additionCommand == null) 
       { 
        additionCommand = new DelegateCommand(param => AddNumbers()); 
       } 

       return additionCommand; 
      } 
     } 

     public void AddNumbers() 
     { 
      Debug.WriteLine ("Addition"); 
      this.CalculatorModel.Result = this.CalculatorModel.Number1 + this.CalculatorModel.Number2; 
      this.Result = this.calculatorModel.Result; 
     } 
    } 

CalculatorModel

public class CalculatorModel : ViewModelBase 
{ 
     private int num1; 
     private int num2; 
     private int result; 

     public CalculatorModel() 
     {} 

     public CalculatorModel (int n1, int n2) 
     { 
      this.Number1 = n1; 
      this.Number2 = n2; 
      this.Result = 0; 
     } 

     public int Number1 
     { 
      get 
      { return num1; } 

      set 
      { 
       if (value != num1) 
       { 
        num1 = value; 
        OnPropertyChanged("Number1"); 
       } 
      } 
     } 

     public int Number2 
     { 
      get 
      { return num2; } 

      set 
      { 
       if (value != num2) 
       { 
        num2 = value; 
        OnPropertyChanged ("Number2"); 
       } 
      } 
     } 

     public int Result 
     { 
      get 
      { return result; } 

      set 
      { 
       if (value != result) 
       { 
        result = value; 
        OnPropertyChanged ("Result"); 
       } 
      } 
     } 
    } 

ViewModelBase

public class ViewModelBase : INotifyPropertyChanged 
    { 
     // event handler 
     public event PropertyChangedEventHandler PropertyChanged; 

     public void OnPropertyChanged (string propertyName) 
     { 
      this.VerifyPropertyName (propertyName); 
      PropertyChangedEventHandler handler = this.PropertyChanged; 

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

     public virtual void VerifyPropertyName(string propertyName) 
     { 
      // Verify that the property name matches a real, 
      // public, instance property on this object. 
      if (TypeDescriptor.GetProperties(this)[propertyName] == null) 
      { 
       string msg = "Invalid property name: " + propertyName; 
       throw new Exception ("Error"); 
      } 
     } 
    } 

DelegateCommand

public class DelegateCommand : ICommand 
{ 
     readonly Action<object>  _execute; 
     readonly Predicate<object> _canExecute; 

     public DelegateCommand (Action<object> execute) : this (execute, null) 
     {} 

     /// <param name="canExecute">The execution status logic.</param> 
     public DelegateCommand (Action<object> execute, Predicate<object> canExecute) 
     { 
      if (execute == null) 
       throw new ArgumentNullException("execute"); 

      _execute = execute; 
      _canExecute = canExecute; 
     } 

     [DebuggerStepThrough] 
     public bool CanExecute(object parameters) 
     { 
      return _canExecute == null ? true : _canExecute(parameters); 
     } 

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

     public void Execute(object parameters) 
     { 
      Debug.WriteLine("Execute"); 
      _execute (parameters); 
     } 
    } 

Answer 1

あなたは値が変更されたとき、プロパティ変更通知を上げない、CalculatorViewModel.Resultに結合されています。 WPFバインディングは通知を使用して、更新する必要があることを認識します。

2種類の溶液：

1. バインドCalculatorViewModel.Result

   <TextBox Name="Answer" Text="{Binding CalculatorModel.Result}" .. /> 
   

2. に代わりのCalculatorModel.Resultしたり、ViewModel.ResultたびModel.Result変更のPropertyChangedイベントを発生させます。例えば

   ：しないように十分な理由がない限り

   public CalculatorModel CalculatorModel 
   { 
       get { return calculatorModel; } 
       set 
       { 
        // remove old event if necessary 
        if (calculatorModel != null) 
         calculatorModel.PropertyChanged -= CalculatorModel_PropertyChanged; 
   
        calculatorModel = value; 
   
        // attach a propertyChanged event to re-raise for ViewModel 
        if (calculatorModel != null) 
         calculatorModel.PropertyChanged += CalculatorModel_PropertyChanged; 
       } 
   } 
   
   private void CalculatorModel_PropertyChanged(object sender, PropertyChangedEventArgs e) 
   { 
       if (e.PropertyName == "Result") 
        OnPropertyChanged("Result"); 
   } 
   

一般的に、私は＃1を使用します。