The OSI PI OPC Server may have several branches. While the branches are returned correctly in the Browser.FetchElements method, the method throws an exception because after the branches are fetched, the code attempts to do a ValidateItems on the branches. The call to ValidateItems throws an exception because the names passed to it are folder names instead of actual tag items.

A simple fix is to test for "isBranch" before making the ValidateITems call, as in the following example:

if (! isBranch)
{
IdentifiedResult[] results = m_server.ValidateItems((ItemIdentifier[])elements.ToArray(typeof(Itemidentifier)));

}