Sort specific objects - vb.net

Question

I have tree classes as follows:
Public Class HtmlSection
Property Name As String
Property SubSections As List(Of HtmlSubSection)
End Class
Public Class HtmlSubSection
Property Name As String
Property SelectedSentences As List(Of HtmlSentence)
End Class
Public Class HtmlSentence
Property Sentence As String
Property Position As Integer
End Class
In below method i am searching for all sentences for each subsection belonging to specific section, at the end i sort those records by Position asc. However sometimes positions have to be changed (directly in sentences) because there could be gaps means after i do OrderBy it will be ordered but it could look like this below. Is there any easy way like linq to change that Positions of that sentences to avoid gaps let's say in the method i shown below.
2
5
77
1001
i would like to change positions starting from 0 in our example:
0
1
2
3
Method:
Public Function GetSelectedSentencesOnSectionLevel(section As HtmlSection) As List(Of HtmlSentence)
Dim sentencesList As New List(Of HtmlSentence)
For Each exSection As HtmlSection In _htmlFactory.SectionsList
If exSection.Name = section.Name Then
Dim sentencesList As New List(Of HtmlSentence)
If Not IsNothing(exSection.SubSections) Then
For Each exSubsection As HtmlSubSection In exSection.SubSections
If Not IsNothing(exSubsection.SelectedSentences) Then
For Each exSentence As HtmlSentence In exSubsection.SelectedSentences
sentencesList.Add(exSentence)
Next
End If
Next
End If
End If
Next
'sort sentences by Posiions ascending
sentencesList = sentencesList.OrderBy(Function(x) x.Position).ToList()
Return sentencesList
End Function
EDIT : more code for helpers:
global class:
Public Class HtmlFactory
Property SectionsList As List(Of HtmlSection)
Sub New()
SectionsList = New List(Of HtmlSection)
End Sub
Sub New(pSectionsList As List(Of HtmlSection))
_SectionsList = pSectionsList
End Sub
Public Sub AddSection(section As HtmlSection)
SectionsList.Add(section)
End Sub
....

Answer 1

Here you are a pure LINQ solution.
Dim index As Integer = -1
Dim sectionName As String
Dim allTheSections As List(Of HtmlSection)
Dim sentenceList = allTheSections _
.Where(Function(sect) _
sect.SubSections IsNot Nothing _
AndAlso sect.Name.Equals(sectionName, StringComparison.OrdinalIgnoreCase)) _
.SelectMany(Function(sect) sect.SubSections) _
.Where(Function(subSect) subSect.SelectedSentences IsNot Nothing) _
.SelectMany(Function(subSect) subSect.SelectedSentences) _
.OrderBy(Function(ss) ss.Position) _
.Select(Function(ss)
index += 1
Return New HtmlSentence With {.Position = index, .Sentence = ss.Sentence}
End Function) _
.ToList()
In this example, allTheSections is where you exSection does coming from.