/// <summary>
/// Verifies that the specified node exists.
/// </summary>
protected override NodeState ValidateNode(
ServerSystemContext context,
NodeHandle handle,
IDictionary <NodeId, NodeState> cache)
{
// not valid if no root.
if (handle == null)
{
return(null);
}
// check if previously validated.
if (handle.Validated)
{
return(handle.Node);
}
NodeState target = null;
// check if already in the cache.
if (cache != null)
{
if (cache.TryGetValue(handle.NodeId, out target))
{
// nulls mean a NodeId which was previously found to be invalid has been referenced again.
if (target == null)
{
return(null);
}
handle.Node = target;
handle.Validated = true;
return(handle.Node);
}
target = null;
}
try
{
// check if the node id has been parsed.
DaParsedNodeId parsedNodeId = handle.ParsedNodeId as DaParsedNodeId;
if (parsedNodeId == null)
{
return(null);
}
NodeState root = null;
DaElement element = null;
ComDaClient client = m_system.SelectClient(context, false);
// validate a branch or item.
if (parsedNodeId.RootType == DaModelUtils.DaElement)
{
element = client.FindElement(parsedNodeId.RootId);
// branch does not exist.
if (element == null)
{
return(null);
}
// create a temporary object to use for the operation.
root = DaModelUtils.ConstructElement(context, element, NamespaceIndex);
root.Handle = element;
AddAdditionalElementReferences(SystemContext, root);
}
// validate an property.
else if (parsedNodeId.RootType == DaModelUtils.DaProperty)
{
element = client.FindElement(parsedNodeId.RootId);
// branch does not exist.
if (element == null)
{
return(null);
}
// validate the property.
DaProperty property = client.FindProperty(parsedNodeId.RootId, parsedNodeId.PropertyId);
// property does not exist.
if (property == null)
{
return(null);
}
// create a temporary object to use for the operation.
root = DaModelUtils.ConstructProperty(context, element.ItemId, property, NamespaceIndex);
root.Handle = property;
AddAdditionalElementReferences(SystemContext, root);
}
// unknown root type.
else
{
return(null);
}
// all done if no components to validate.
if (String.IsNullOrEmpty(parsedNodeId.ComponentPath))
{
handle.Validated = true;
handle.Node = target = root;
return(handle.Node);
}
// validate component.
NodeState component = root.FindChildBySymbolicName(context, parsedNodeId.ComponentPath);
// component does not exist.
if (component == null)
{
return(null);
}
// found a valid component.
handle.Validated = true;
handle.Node = target = component;
return(handle.Node);
}
finally
{
// store the node in the cache to optimize subsequent lookups.
if (cache != null)
{
cache.Add(handle.NodeId, target);
}
}
}
