Liaison de données WPF avec plusieurs dépendances?

Question

Je crois que ce code peut nécessiter plus d'efforts pour comprendre que la moyenne, donc j'utilise des commentaires de code contextuels pour expliquer ma situation dans le but de faciliter la compréhension de ma question.

public class MyControl : System.Windows.FrameworkElement 
{ 
    public double Property1 { get; set; } 
    public double Property2 { get; set; } 
} 

...

<StackPanel> 
    <local:MyControl Name="ControlA" /> 
    <local:MyControl Name="ControlB" /> 
    <!--We want to use data-binding to force ControlA.MinWidth to be equal to 
     ControlA.Property1 * ControlB.Property2 at all times--> 
</StackPanel> 

...

static readonly MyPrimaryConverter PrimConv = new MyPrimaryConverter(); 
static readonly MySecondaryConverter SecConv = new MySecondaryConverter(); 

public Window1() 
{ 
    InitializeComponent(); 

    System.Windows.Data.BindingExpressionBase BindExp1, BindExp2; 
    System.Windows.Data.Binding MyBinding; 

    MyBinding = new System.Windows.Data.Binding("Property1"); 
    MyBinding.Source = ControlA; 
    MyBinding.Mode = System.Windows.Data.BindingMode.OneWay; 
    MyBinding.Converter = PrimConv; 
    MyBinding.ConverterParameter = ControlB; 
    BindExp1 = ControlA.SetBinding(
         System.Windows.UIElement.MinWidthProperty, MyBinding); 
    //Binds correctly and shows "Status" as active 

    MyBinding = new System.Windows.Data.Binding("Property2"); 
    MyBinding.Source = ControlB; // ControlB.Property2 is the source value now 
    MyBinding.Mode = System.Windows.Data.BindingMode.OneWay; 
    MyBinding.Converter = SecConv; //Uses the secondary converter 
    MyBinding.ConverterParameter = ControlA; //ControlA is the parameter now 
    BindExp2 = ControlA.SetBinding(
         System.Windows.UIElement.MinWidthProperty, MyBinding); 
    /* Also binds correctly and shows "Status" as active, 
     but causes BindExp1 to show "Status" as "Detached" 

     ****THIS IS THE PROBLEM I NEED HELP WITH**** 

     How can I successfully bind ControlA.MinWidth to BOTH of the values 
     that are used to calculate MinWidth? 

     This is required so that MinWidth will be recalculated if EITHER 
     value changes at any time 

     Bonus points if you can show how to do it with 
     only one converter class instead of two */ 
} 

...

[System.Windows.Data.ValueConversion(typeof(double), typeof(double))] 
public class MyPrimaryConverter : System.Windows.Data.IValueConverter 
{ 
    public object Convert( object value, System.Type targetType, 
         object parameter, System.Globalization.CultureInfo culture) 
    { 
     if ((value is double) && (parameter is MyControl)) 
      return ((double)value) * (parameter as MyControl).Property2; 
      /* This converter ALWAYS returns: 
       ControlA.Property1 * ControlB.Property2 
       value == ControlA.Property1 and parameter == ControlB, 
       so we return value * parameter.Property2 */ 

     return System.Windows.DependencyProperty.UnsetValue; 
    } 

    public object ConvertBack( object value, System.Type targetType, 
         object parameter, System.Globalization.CultureInfo culture) 
    { return System.Windows.DependencyProperty.UnsetValue; } 
} 

[System.Windows.Data.ValueConversion(typeof(double), typeof(double))] 
public class MySecondaryConverter : System.Windows.Data.IValueConverter 
{ 
    public object Convert( object value, System.Type targetType, 
         object parameter, System.Globalization.CultureInfo culture) 
    { 
     if ((value is double) && (parameter is MyControl)) 
      return ((double)value) * (parameter as MyControl).Property1; 
      /* This converter also ALWAYS returns: 
       ControlA.Property1 * ControlB.Property2 
       "value" and "parameter" are swapped: 
       value == ControlB.Property2 and parameter == ControlA 
       so we return value * parameter.Property1 
       instead of value * parameter.Property2 */ 

     return System.Windows.DependencyProperty.UnsetValue; 
    } 

    public object ConvertBack( object value, System.Type targetType, 
         object parameter, System.Globalization.CultureInfo culture) 
    { return System.Windows.DependencyProperty.UnsetValue; } 
} 

Answer 1

Je pense que vous devez utiliser un MultiValueConverter