protected Binding CreateTheBinding(BindingTarget bindingTarget, MyBindingInfo bInfo, Type sourceType,
OSCollection pathListeners, out bool isCustom)
{
System.Diagnostics.Debug.Assert(sourceType != null, "The SourceType should never be null here.");
// One node: 1 parent, 0 intervening objects, the terminal path element is "." -- The binding binds to the source data itself.
// Two nodes: 1 parent, 0 intervening objects, 1 terminal path element.
// Three nodes: 1 parent, 1 intervening object, 1 terminal path element.
// Four nodes: 1 parent, 2 intervening objects, 1 terminal path element.
// The next to last node, must have data, in order to avoid binding warnings.
ObservableSource lastParent = pathListeners[pathListeners.Count - 2];
string strNewPath = pathListeners.GetNewPath(justForDiag: false);
ObservableSourceStatusEnum lastParentStatus = lastParent.Status;
System.Diagnostics.Debug.WriteLine($"Path = {bInfo.PropertyPath.Path}, NewPath = {strNewPath}, " +
$"Terminal Node Status = {lastParentStatus}.");
if (lastParentStatus.IsReadyOrWatching())
{
// Check to see if DataContext holds source property.
// When a DataContext is set via a binding, in some cases,
// bindings that rely on that DataContext may get set
// before the binding that provides the correct DataContext is set.
ObservableSource root = pathListeners[ROOT_INDEX];
if (root.SourceKind == SourceKindEnum.FrameworkElement || root.SourceKind == SourceKindEnum.FrameworkContentElement)
{
string firstChildPathElement = pathListeners[ROOT_INDEX + 1].PathElement;
if (!root.DoesChildExist(firstChildPathElement))
{
System.Diagnostics.Debug.WriteLine($"No Binding is being created. Data is present, but doesn't contain source property: {firstChildPathElement}.");
isCustom = false;
return(null);
}
}
// TODO: What about the original PropertyPath parameters?
PropertyPath newPath = new PropertyPath(strNewPath);
isCustom = lastParent.IsPropBagBased; // .IsPropBagBasedAndNoCustomTypeDescriptors;
return(CreateBinding(bindingTarget, bInfo, sourceType, newPath, isCustom));
}
else
{
System.Diagnostics.Debug.Assert(pathListeners[0].IsListeningForNewDC, "There are no active listeners!");
System.Diagnostics.Debug.WriteLine("No Binding is being created, not enough data.");
isCustom = false;
return(null);
}
}
protected virtual void DataSourceHasChanged(object sender, DataSourceChangedEventArgs e)
{
BindingBase oldBinding;
if (BindingTarget.IsDependencyProperty)
{
oldBinding = GetTheBindingBase(BindingTarget.DependencyObject, BindingTarget.DependencyProperty);
}
else
{
oldBinding = null;
}
bool hadBinding = oldBinding != null;
if (!e.DataWasUpdated && oldBinding != null)
{
return;
}
ObservableSource os = (ObservableSource)sender;
bool bindingInfoChanged = RefreshPathListeners(BindingTarget, BindingInfo, SourceType,
_dataSourceChangeListeners, e, os);
if (!bindingInfoChanged && oldBinding != null)
{
return;
}
Binding newBinding = CreateTheBinding(BindingTarget, BindingInfo, SourceType,
_dataSourceChangeListeners, out bool isCustom);
if (hadBinding && BindingTarget.IsDependencyProperty)
{
ClearTheBinding(BindingTarget.DependencyObject, BindingTarget.DependencyProperty);
}
if (newBinding != null)
{
try
{
//BindingExpressionBase bExp = BindingOperations.SetBinding(_targetObject,
// _targetProperty, newBinding);
if (BindingTarget.IsDependencyProperty)
{
ClearTheBinding(BindingTarget.DependencyObject, BindingTarget.DependencyProperty);
BindingExpressionBase bExp = SetTheBinding(BindingTarget.DependencyObject, BindingTarget.DependencyProperty, newBinding);
string bType = isCustom ? "PropBag-Based" : "Standard";
System.Diagnostics.Debug.WriteLine($"CREATING {bType} BINDING from {newBinding.Path.Path} to {BindingTarget.PropertyName} on object: {BindingTarget.ObjectName}.");
}
}
catch
{
System.Diagnostics.Debug.WriteLine("Attempt to SetBinding failed.");
}
if (hadBinding)
{
System.Diagnostics.Debug.WriteLine($"{BinderName} set a new binding on some target that is replacing an existing binding.");
}
else
{
System.Diagnostics.Debug.WriteLine($"{BinderName} set a new binding on some target that had no binding previously.");
}
}
else
{
if (hadBinding)
{
System.Diagnostics.Debug.WriteLine($"{BinderName} removed binding on some target and replaced it with no binding.");
}
}
}
protected bool RefreshPathListeners(BindingTarget bindingTarget, MyBindingInfo bInfo, Type sourceType, OSCollection pathListeners,
DataSourceChangedEventArgs changeInfo, ObservableSource signalingOs)
{
// Assume that this operation will not require the binding to be updated,
// until proven otherwise.
bool bindingInfoChanged = false;
int nodeIndex = _dataSourceChangeListeners.IndexOf(signalingOs);
if (nodeIndex == -1)
{
throw new InvalidOperationException($"Could not get pointer to path element while processing " +
$"DataSourceChanged event for {BinderName} in PropBagControlsWPF.Binders.");
}
ObservableSource parentOs = pathListeners[nodeIndex];
ObservableSourceStatusEnum status;
// Initializing
// Attempt to get a reference to the Source Root (Object with DataContext property or DataSourceProvider.)
if (changeInfo.ChangeType == DataSourceChangeTypeEnum.Initializing)
{
System.Diagnostics.Debug.Assert(nodeIndex == ROOT_INDEX, $"The node index should refer to the ObservableSource for " +
$"the root when DataSourceChangeType = {nameof(DataSourceChangeTypeEnum.Initializing)}.");
string rootElementName = GetRootPathElementName(pathListeners);
ObservableSourceProvider osp = GetSourceRoot(bindingTarget, bInfo.Source, rootElementName, BinderName);
if (osp == null)
{
throw new InvalidOperationException($"{BinderName} could not locate a data source.");
}
status = pathListeners.ReplaceListener(ROOT_INDEX, ref osp, this.DataSourceHasChanged,
out parentOs);
if (parentOs?.IsListeningForNewDC != true)
{
throw new InvalidOperationException($"{BinderName} could not locate a data source.");
}
}
// DataContextUpdated
// Refresh the Source Root
else if (changeInfo.ChangeType == DataSourceChangeTypeEnum.DataContextUpdated)
{
System.Diagnostics.Debug.Assert(nodeIndex == ROOT_INDEX, $"The node index should refer to the ObservableSource for" +
$" the root when DataSourceChangeType = {nameof(DataSourceChangeTypeEnum.DataContextUpdated)}.");
status = parentOs.Status;
pathListeners.ResetListeners(ROOT_INDEX + 1, this.DataSourceHasChanged);
bindingInfoChanged = true;
}
// Handle Collection Change
else if (changeInfo.ChangeType == DataSourceChangeTypeEnum.CollectionChanged)
{
return(bindingInfoChanged);
}
// Handle Property Changed
else if (changeInfo.ChangeType == DataSourceChangeTypeEnum.PropertyChanged)
{
// The PropModel of the value of this node's child may have changed.
// Replace the child with a new SourceListner, if appropriate
// and then fall-through to normal processing, at signaled step + 2.
string changedPropName = changeInfo.PropertyName;
nodeIndex++;
ObservableSource child = pathListeners[nodeIndex];
bool matched =
changedPropName == child.NewPathElement ||
changedPropName == "Item[]" && child.NewPathElement.StartsWith("[");
if (!matched || !(nodeIndex < pathListeners.Count - 1))
{
// Action is not required if
// The updated property is not part of our path,
// or our child in the terminal node,
return(bindingInfoChanged);
}
// Replace the child, if
// 1. It was null and now is not, or
// 2. It is now null and was not null, or
// 3. It was PropBag-based and is now is not, or
// 4. It was a regular CLR object and is now PropBag-based, or
// 5. It is still PropBag-Based and the prop item corresponding
// to the grandchild node had a change in type.
if (!child.Status.IsReadyOrWatching())
{
string prevValueForNewPathElement = child.NewPathElement;
ObservableSourceProvider newChildProvider = parentOs.GetChild(child.PathElement);
if (newChildProvider?.Data == null)
{
// Still no data ??
System.Diagnostics.Debug.WriteLine("Child was null and is still null.");
//ResetPathListeners(pathListeners, nodeIndex);
pathListeners.ResetListeners(nodeIndex, this.DataSourceHasChanged);
bindingInfoChanged = true;
return(bindingInfoChanged);
}
//ObservableSourceStatusEnum newCStatus =
// ReplaceListener(pathListeners, nodeIndex, ref newChildProvider,
// this.DataSourceHasChanged, out ObservableSource newChild);
ObservableSourceStatusEnum newCStatus = pathListeners.ReplaceListener(nodeIndex, ref newChildProvider,
this.DataSourceHasChanged, out ObservableSource newChild);
if (newChild != null)
{
string newPathElement = GetNewPathElement(newChild.PathElement, newChild.Type, parentOs.IsPropBagBased);
newChild.NewPathElement = newPathElement;
bindingInfoChanged = (newPathElement != prevValueForNewPathElement);
}
}
// If the child was updated, begin processing our grand children.
parentOs = pathListeners[nodeIndex];
status = parentOs?.Status ?? ObservableSourceStatusEnum.NoType;
}
else
{
throw new ApplicationException($"The DataSourceChangedType: {changeInfo.ChangeType} is not recognized.");
}
// Now, starting at step: stepNo + 1, replace or refresh each listener.
int nPtr = nodeIndex + 1;
for (; nPtr < pathListeners.Count - 1 && status.IsReadyOrWatching(); nPtr++)
{
// This is an itermediate step and the path has at least two components.
parentOs.BeginListeningToSource();
if (nPtr > 1)
{
// Make sure we are listening to events that this ObservableSource may raise.
// We know that we are subscribed to the root.
parentOs.Subscribe(this.DataSourceHasChanged);
}
string pathElement = pathListeners[nPtr].PathElement;
string prevValueForNewPathElement = pathListeners[nPtr].NewPathElement;
ObservableSourceProvider osp = parentOs.GetChild(pathElement);
//status = ReplaceListener(pathListeners, nPtr, ref osp, this.DataSourceHasChanged,
// out ObservableSource os);
status = pathListeners.ReplaceListener(nPtr, ref osp, this.DataSourceHasChanged,
out ObservableSource os);
if (os != null)
{
string newPathElement = GetNewPathElement(pathElement, os.Type, parentOs.IsPropBagBased);
os.NewPathElement = newPathElement;
bindingInfoChanged = (newPathElement != prevValueForNewPathElement);
}
// Note: if os is null, status will be "NoType", i.e. not ready.
if (status == ObservableSourceStatusEnum.Ready)
{
System.Diagnostics.Debug.WriteLine($"Listener for {pathElement} is ready.");
}
else
{
System.Diagnostics.Debug.WriteLine($"Listener for {pathElement} is not ready.");
}
parentOs = os;
//status = os.Status; -- Not needed, ReplaceListener sets this variable.
}
if (nPtr == pathListeners.Count - 1)
{
// Process terminal node.
ObservableSource lastNode = pathListeners[nPtr];
if (status.IsReadyOrWatching())
{
string newPathElement = GetNewPathElement(lastNode.PathElement, lastNode.Type, parentOs.IsPropBagBased);
if (lastNode.NewPathElement != newPathElement)
{
lastNode.NewPathElement = newPathElement;
bindingInfoChanged = true;
}
if (!status.IsWatching())
{
parentOs.BeginListeningToSource();
}
}
}
else
{
// Don't have all of the data present required to create a binding.
System.Diagnostics.Debug.WriteLine($"RefreshPathListeners claims that no binding should be created for path = {bInfo.PropertyPath.Path}.");
//ResetPathListeners(pathListeners, nPtr);
pathListeners.ResetListeners(nPtr, this.DataSourceHasChanged);
}
return(bindingInfoChanged);
}
