=> target.DataContextChanged -= DatacontextTarget_DataContextChanged; // free up event handlers.
/// <summary>
/// Called whenever the datacontext of one of the inner source binding changed.
/// </summary>
/// <param name="sender">A framework element for which the property changed.</param>
/// <param name="e">Information about the datacontext changed event.</param>
private void DatacontextTarget_DataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
{
if (TargetObject == sender && TargetProperty != null)
{
ToggleBinding(BindingHelpers.GetBindingSource(innerBinding, TargetObject, out bool _, out bool _));
}
else if (sender is FrameworkElement casted)
{
casted.DataContextChanged -= DatacontextTarget_DataContextChanged;
}
}
protected override void OnTargetLoaded(FrameworkElement target) => Initialize(); // retry class initialization at loaded.
/// <summary>
/// Prepares this class to filter data based on resolved (or unresolved source).
/// </summary>
private void Initialize()
{
if (initialized)
{
return;
}
// Find source value here if not provided:
var source = BindingHelpers.GetBindingSource(innerBinding, TargetObject, out bool resolved, out bool _);
if (resolved)
{
Initialize(source);
}
}
/// <summary>
/// Called whenever the datacontext of target object changed.
/// </summary>
/// <param name="sender">A framework element for which the property changed.</param>
/// <param name="e">Information about the datacontext changed event.</param>
private void DatacontextTarget_DataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
{
if (TargetObject == sender && TargetProperty != null)
{
if (bindingWatcher != null)
{
bindingWatcherDescriptor.RemoveValueChanged(bindingWatcher, BindingWatcher_SourcePropertyChanged);
bindingWatcher.Dispose();
}
bindingWatcher = new DependencyPropertyWatcher <object>(BindingHelpers.GetBindingSource(InnerBinding, TargetObject, out bool _, out bool _), InnerBinding.Path);
bindingWatcherDescriptor = bindingWatcherDescriptor = DependencyPropertyDescriptor.FromProperty(DependencyPropertyWatcher <object> .ValueProperty, typeof(DependencyPropertyWatcher <object>));
bindingWatcherDescriptor.AddValueChanged(bindingWatcher, BindingWatcher_SourcePropertyChanged);
}
else if (sender is FrameworkElement casted)
{
casted.DataContextChanged -= DatacontextTarget_DataContextChanged;
}
}
/// <summary>
/// Resolves path binding and prepares the inner custom binding with resolved path value.
/// </summary>
/// <param name="serviceProvider">Service provider given by the framework.</param>
/// <returns>True if successfully prepared path binding, false if cannot resolve its value.</returns>
private bool ResolveBoundPathBinding(IServiceProvider serviceProvider = null)
{
if (PathValueBinding == null)
{
return(false);
}
// If source is not already resolved:
if (boundPathSource == null)
{
// Try to get the source of value for the path value binding using base mechanisms:
boundPathSource = serviceProvider != null?BindingHelpers.GetBindingSource(PathValueBinding, serviceProvider, out bool source_is_resolved, out bool source_is_datacontext)
: BindingHelpers.GetBindingSource(PathValueBinding, TargetObject, out source_is_resolved, out source_is_datacontext);
if (!source_is_resolved || boundPathSource == null)
{
return(false);
}
// If source is datacontext then track it for future changes:
if (source_is_datacontext)
{
(TargetObject as FrameworkElement).DataContextChanged += TargetObject_DataContextChanged;
}
}
// Try to resolve path binding value on the source:
var value = BindingHelpers.ResolvePathValue(boundPathSource, PathValueBinding.Path);
// If not given a proper property path format:
if (!(value is string) && !(value is PropertyPath))
{
StopTrackingPathBindingUpdates(); // as we did not resolved binding, stop tracking changes on current bind if any.
return(false);
}
// Update bound path binding by getting a copy of the precedent value:
if (!providing_value)
{
boundPathBinding = boundPathBinding?.Clone();
if (boundPathBinding == null)
{
return(false);
}
}
// Build new inner binding path based on resolved value + OverridePath property:
if (value is string as_string)
{
if (!OverridePath && Path != null)
{
boundPathBinding.Path = new PropertyPath(Path.Path + "." + as_string); // TODO: path parameters?
}
else
{
boundPathBinding.Path = new PropertyPath(as_string);
}
}
else if (value is PropertyPath asPropertyPath)
{
if (!OverridePath && Path != null)
{
boundPathBinding.Path = new PropertyPath(Path.Path + "." + asPropertyPath.Path, asPropertyPath.PathParameters);
}
else
{
boundPathBinding.Path = asPropertyPath;
}
}
// As we resolved binding, track any further changes:
StartTrackingPathBindingUpdates();
return(true);
}
