If the ID is {\it NULL} the wxDataViewItem is invalid and
\helpref{IsOk}{wxdataviewitemisok} will return {\it false}
which used in many places in the API of wxDataViewCtrl
-to indicate that e.g. no item was found etc.
+to indicate that e.g. no item was found. An ID of NULL
+is also used to indicate the invisible root. Examples
+for this are
+\helpref{wxDataViewModel::GetParent}{wxdataviewmodelgetparent} and
+\helpref{wxDataViewModel::GetChildren}{wxdataviewmodelgetchildren}.
+
\wxheading{Derived from}
<dataview.h>
-\wxheading{Data structures}
+\wxheading{Library}
-\latexignore{\rtfignore{\wxheading{Members}}}
+\helpref{wxAdv}{librarieslist}
\membersection{wxDataViewItem::wxDataViewItem}\label{wxdataviewitemwxdataviewitem}
Returns true if the ID is not {\it NULL}.
-\membersection{wxDataViewItem::void*}\label{wxdataviewitemvoid*}
+\membersection{wxDataViewItem::void*}\label{wxdataviewitemvoid}
\constfunc{operator const}{void*}{\void}