//======================================================================
// BrowseNext
/// <summary>
/// Continues browsing the server's address space at the specified position.
/// </summary>
/// <param name="maxElements">The maximum number of elements to return.</param>
/// <param name="position">The position object used to continue a browse operation.</param>
/// <returns>The set of elements that meet the filter criteria.</returns>
public TsCHdaBrowseElement[] BrowseNext(int maxElements, ref IOpcBrowsePosition position)
{
// check arguments.
if (position == null || position.GetType() != typeof(BrowsePosition))
{
throw new ArgumentException("Not a valid browse position object.", nameof(position));
}
// interpret invalid values as 'no limit'.
if (maxElements <= 0)
{
maxElements = Int32.MaxValue;
}
lock (this)
{
BrowsePosition pos = (BrowsePosition)position;
ArrayList elements = new ArrayList();
if (!pos.FetchingItems)
{
elements = FetchElements(pos.Enumerator, maxElements, true);
// check if max element count reached.
if (elements.Count >= maxElements)
{
return((TsCHdaBrowseElement[])elements.ToArray(typeof(TsCHdaBrowseElement)));
}
// release enumerator.
pos.Enumerator.Dispose();
pos.Enumerator = null;
pos.FetchingItems = true;
// move to the correct position in the server's address space.
try
{
m_browser.ChangeBrowsePosition(OPCHDA_BROWSEDIRECTION.OPCHDA_BROWSE_DIRECT, pos.BranchPath);
}
catch (Exception e)
{
throw Utilities.Interop.CreateException("IOPCHDA_Browser.ChangeBrowsePosition", e);
}
// create enumerator for items.
pos.Enumerator = GetEnumerator(false);
}
// fetch next set of items.
ArrayList items = FetchElements(pos.Enumerator, maxElements - elements.Count, false);
if (items != null)
{
elements.AddRange(items);
}
// check if max element count reached.
if (elements.Count >= maxElements)
{
return((TsCHdaBrowseElement[])elements.ToArray(typeof(TsCHdaBrowseElement)));
}
// release position object.
position.Dispose();
position = null;
// return elements.
return((TsCHdaBrowseElement[])elements.ToArray(typeof(TsCHdaBrowseElement)));
}
}
/// <summary>
/// Begins a browsing the server's address space at the specified branch.
/// </summary>
/// <param name="itemID">The item id of the branch to search.</param>
/// <param name="maxElements">The maximum number of elements to return.</param>
/// <param name="position">The position object used to continue a browse operation.</param>
/// <returns>The set of elements that meet the filter criteria.</returns>
public TsCHdaBrowseElement[] Browse(OpcItem itemID, int maxElements, out IOpcBrowsePosition position)
{
position = null;
// interpret invalid values as 'no limit'.
if (maxElements <= 0)
{
maxElements = Int32.MaxValue;
}
lock (this)
{
string branchPath = (itemID != null && itemID.ItemName != null)?itemID.ItemName:"";
// move to the correct position in the server's address space.
try
{
m_browser.ChangeBrowsePosition(OPCHDA_BROWSEDIRECTION.OPCHDA_BROWSE_DIRECT, branchPath);
}
catch (Exception e)
{
throw Utilities.Interop.CreateException("IOPCHDA_Browser.ChangeBrowsePosition", e);
}
// browse for branches
EnumString enumerator = GetEnumerator(true);
ArrayList elements = FetchElements(enumerator, maxElements, true);
// check if max element count reached.
if (elements.Count >= maxElements)
{
position = new BrowsePosition(branchPath, enumerator, false);
return((TsCHdaBrowseElement[])elements.ToArray(typeof(TsCHdaBrowseElement)));
}
// release enumerator.
enumerator.Dispose();
// browse for items
enumerator = GetEnumerator(false);
ArrayList items = FetchElements(enumerator, maxElements - elements.Count, false);
if (items != null)
{
elements.AddRange(items);
}
// check if max element count reached.
if (elements.Count >= maxElements)
{
position = new BrowsePosition(branchPath, enumerator, true);
return((TsCHdaBrowseElement[])elements.ToArray(typeof(TsCHdaBrowseElement)));
}
// release enumerator.
enumerator.Dispose();
return((TsCHdaBrowseElement[])elements.ToArray(typeof(TsCHdaBrowseElement)));
}
}
