/// <summary> Implements the functionality documented in the other overloads. </summary>
private static void Bind(INotifyPropertyChanged source, string propertyName, string propertyOnPropertyName, PropertyChangedEventHandler handler, object defaultValue, Type propertyOnPropertyType)
{
Contract.Requires(source != null);
Contract.Requires(handler != null);
Contract.Requires(source.GetType().GetProperty(propertyName) != null);
var sourceProperty = GetProperty(source.GetType(), propertyName);
var sourcePropertyType = GetPropertyType(source.GetType(), propertyName);
Contract.Requires(sourcePropertyType.Implements(typeof(INotifyPropertyChanged)), $"The property on the source must implement '{nameof(INotifyPropertyChanged)}'");
Contract.Requires(GetPropertyType(sourcePropertyType, propertyOnPropertyName) != null, $"Property '{propertyName}' was not found on type '{sourcePropertyType.Name}'");
Contract.Requires(propertyOnPropertyType.IsAssignableFrom(GetPropertyType(sourcePropertyType, propertyOnPropertyName)));
Contract.Requires(propertyOnPropertyType.IsInstanceOfType(defaultValue) || (ReferenceEquals(defaultValue, null) && !propertyOnPropertyType.IsValueType));
handler = handler.FilterOn(propertyOnPropertyName);
PropertyChangedEventHandler onSourcePropertyChanged = (sender, eventArg) =>
{
Contract.Requires(eventArg is IPropertyMutatedEventArgs);
var e = (IPropertyMutatedEventArgs)eventArg;
var oldSource = (INotifyPropertyChanged)e.OldValue;
if (oldSource != null)
{
oldSource.PropertyChanged -= handler;
}
var newSource = (INotifyPropertyChanged)e.NewValue;
if (newSource != null)
{
newSource.PropertyChanged += handler;
}
var oldValue = GetPropertyValue(oldSource, propertyOnPropertyName, defaultValue: defaultValue);
var newValue = GetPropertyValue(newSource, propertyOnPropertyName, defaultValue: defaultValue);
if (!Equals(oldValue, newValue)) // uses virtual method oldValue.Equals(object)
{
handler(newSource ?? oldSource, PropertyMutatedEventArgsExtensions.Create(propertyOnPropertyName, propertyOnPropertyType, oldValue, newValue));
}
};
source.PropertyChanged += onSourcePropertyChanged.FilterOn(propertyName);
object currentValue = sourceProperty.GetValue(source);
// onSourcePropertyChanged is invoked regardless of whether currentValue equals sourcePropertyType.GetDefault()
// because it hooks the handler onto currentValue.PropertyChange
onSourcePropertyChanged(source, PropertyMutatedEventArgsExtensions.Create(propertyName, sourcePropertyType, sourcePropertyType.GetDefault(), currentValue));
}
