<Extension()>
Public Function HasNull(dataTable As DataTable) As Boolean
    If dataTable Is Nothing Then
        Throw New ArgumentNullException("dataTable must be initialized", "dataTable")
    End If
    Dim allColumns = dataTable.Columns.Cast(Of DataColumn).ToList() ' materialize
    Dim hasNullField As Boolean = dataTable.AsEnumerable().
        Any(Function(row) allColumns.Any(Function(c) row.IsNull(c)))
    Return hasNullField
End Function