/// <summary>
/// Returns the set of elements in the address space that meet the specified criteria.
/// </summary>
public Opc.Da.BrowseElement[] Browse(
ItemIdentifier itemID,
BrowseFilters filters,
ref Opc.Da.BrowsePosition position)
{
lock (this)
{
if (m_disposed) throw new ObjectDisposedException("Opc.Da.Cache");
BrowseElement element = m_addressSpace;
// find desired element.
string browsePath = (itemID != null)?itemID.ItemName:null;
if (browsePath != null && browsePath.Length > 0)
{
element = m_addressSpace.Find(browsePath);
if (element == null)
{
// check if browsing a property item.
PropertyID property = Property.VALUE;
string rootID = LookupProperty(browsePath, out property);
if (rootID != null)
{
element = m_addressSpace.Find(rootID);
}
if (element == null)
{
throw new ResultIDException(ResultID.Da.E_UNKNOWN_ITEM_NAME);
}
// property items never contain children.
return new Opc.Da.BrowseElement[0];
}
}
// check if no elements exist.
if (element.Count == 0)
{
return new Opc.Da.BrowseElement[0];
}
// determine start position.
int start = 0;
if (position != null)
{
start = ((BrowsePosition)position).Index;
position.Dispose();
position = null;
}
// process child nodes.
ArrayList results = new ArrayList();
for (int ii = start; ii < element.Count; ii++)
{
BrowseElement child = element.Child(ii);
// exclude elements without children.
if (filters.BrowseFilter == browseFilter.branch && child.Count == 0)
{
continue;
}
// check if an element is an item.
CacheItem item = (CacheItem)m_items[child.ItemID];
// exclude elements which are not items.
if (filters.BrowseFilter == browseFilter.item && item == null)
{
continue;
}
// apply name filter (using the SQL LIKE operator).
if (filters.ElementNameFilter != null && filters.ElementNameFilter.Length > 0)
{
if (!Opc.Convert.Match(child.Name, filters.ElementNameFilter, true))
{
continue;
}
}
// add element to list of results.
Opc.Da.BrowseElement result = new Opc.Da.BrowseElement();
result.Name = child.Name;
result.ItemName = child.ItemID;
result.ItemPath = null;
result.IsItem = item != null;
result.HasChildren = child.Count > 0;
result.Properties = null;
// add properties to results.
if (filters.ReturnAllProperties || filters.PropertyIDs != null)
{
result.Properties = GetProperties(item, (filters.ReturnAllProperties)?null:filters.PropertyIDs, filters.ReturnPropertyValues);
}
results.Add(result);
// check if max elements exceeded.
if (filters.MaxElementsReturned > 0 && results.Count >= filters.MaxElementsReturned)
{
if (ii+1 < element.Count)
{
position = new BrowsePosition(itemID, filters);
((BrowsePosition)position).Index = ii+1;
}
break;
}
}
// return results.
return (Opc.Da.BrowseElement[])results.ToArray(typeof(Opc.Da.BrowseElement));
}
}
