Comment vérifier si un objet de dépendance contient une propriété de dépendance?

Question

Essentiellement, je veux une réflexion simple où j'ai un DependencyProperty arbitraire en tant que paramètre. J'aurais un cas particulier (dans une instruction if, par exemple) si DependencyProperty est défini par/property d'un PlaneProjection. J'ai fait un simple fandangling de GetType() mais pas de chance avec les getters attendus comme MemberType.

public void SomeFunc(DependencyProperty dp) 
{ 
    // if dp is a dependency property of plane projection, do something 
    // would maybe look like PlaneProjection.hasProperty(dp) 
} 

Answer 1

Essayez ce code avec des méthodes d'extension:

public static class Helpers 
{ 
    public static DependencyProperty FindDependencyProperty(this DependencyObject target, string propName) 
    { 
     FieldInfo fInfo = target.GetType().GetField(propName, BindingFlags.Static | BindingFlags.FlattenHierarchy | BindingFlags.Public); 

     if (fInfo == null) return null; 

     return (DependencyProperty)fInfo.GetValue(null); 
    } 

    public static bool HasDependencyProperty(this DependencyObject target, string propName) 
    { 
     return FindDependencyProperty(target, propName) != null; 
    } 

    public static string GetStaticMemberName<TMemb>(Expression<Func<TMemb>> expression) 
    { 
     var body = expression.Body as MemberExpression; 

     if (body == null) throw new ArgumentException("'expression' should be a member expression"); 

     return body.Member.Name; 
    } 
} 

Utilisation:

planeProjection1.HasDependecyProperty(
    Helpers.GetStaticMemberName(() => PlaneProjection.CenterOfRotationXProperty)); 

Answer 2

Est-ce que cette condition l'attrape?

Modifier: uniquement dans WPF - pas SilverLight.

dp.OwnerType.IsAssignableFrom(typeof(PlaneProjection)) 

Answer 3

Cela devrait prendre soin de vos besoins en SilverLight:

private static readonly Dictionary<DependencyProperty, Type> _ownerCache = new Dictionary<DependencyProperty, Type>(); 
// normally you'd use a HashSet<DependencyProperty>, but it's not available in SilverLight 
private static readonly Dictionary<Type, Dictionary<DependencyProperty, bool>> _excludeCache = new Dictionary<Type, Dictionary<DependencyProperty, bool>>(); 

public static bool IsOwnedByTypeOrParent(DependencyProperty dp, Type type) 
{ 
    lock (_ownerCache) 
    { 
     Type owner; 
     if (_ownerCache.TryGetValue(dp, out owner)) 
      return owner.IsAssignableFrom(type); 

     Dictionary<DependencyProperty, bool> exclude; 
     if (_excludeCache.TryGetValue(type, out exclude)) 
     { 
      if (exclude.ContainsKey(dp)) 
       return false; 
     } 

     FieldInfo[] fields = type.GetFields(BindingFlags.Static | BindingFlags.FlattenHierarchy); 
     foreach (FieldInfo field in fields) 
     { 
      if (typeof(DependencyProperty).IsAssignableFrom(field.FieldType)) 
      { 
       try 
       { 
        object value = field.GetValue(null); 
        if (object.ReferenceEquals(dp, value)) 
        { 
         _ownerCache[dp] = field.DeclaringType; 
         return true; 
        } 
       } 
       catch 
       { 
       } 
      } 
     } 

     if (exclude == null) 
     { 
      exclude = new Dictionary<DependencyProperty, bool>(); 
      _excludeCache[type] = exclude; 
     } 

     exclude.Add(dp, false); 

     /* optional if you want to minimize memory overhead. unnecessary unless 
     * you are using this on enormous numbers of types/DPs 
     */ 
     foreach (var item in _excludeCache) 
     { 
      item.Value.Remove(dp); 
     } 

     return false; 
    } 
}