How to implement lazy loading in listview wpf VB.net - wpf

Question

I'm newbie, I've a XAML file and code behind's, its load all data but I will lazy loading. I binding data in listview. I tried searching but did not produce the expected results, so there is no way that can be done.
code behind:
Public Sub MappingThumbnailSearchResult(thumbSearchResult As VI_ThumbnailSearchResultResponse, token As CancellationToken, ByRef dataDic As Dictionary(Of String, ObservableCollection(Of Object)))
Dim data As List(Of Object) = New List(Of Object)
Try
If thumbSearchResult.result_body Is Nothing OrElse thumbSearchResult.result_body.search_result Is Nothing Then Exit Sub
For Each item In thumbSearchResult.result_body.search_result
Try
If token.IsCancellationRequested Then Exit Sub
Dim thumbnailKey As String = ""
If Not item.thumbnail_key.Contains("\\") Then
thumbnailKey = item.thumbnail_key.ToString().Replace("\", "\\")
Else
thumbnailKey = item.thumbnail_key
End If
Dim imageResult = RequestAPI.GetInstance.GetThumbnailBase64(New VI_ThumbnailRequest With {.ThumbnailKey = thumbnailKey})
Dim hasThumb As Boolean = False
If imageResult IsNot Nothing Then
If imageResult.result_body.thumbnail IsNot Nothing Then
hasThumb = True
Dim base64Str As String = imageResult.result_body.thumbnail
item.thumbnail_base64 = imageResult.result_body.thumbnail
item.thumbnail_bitmap = BaseViewModel.BitmapFromSource(BaseViewModel.Base64ToImage(base64Str))
End If
End If
If Not hasThumb Then
'default image if have error when get thumbnail image
If item.system_type.Equals(EnumType.SystemType.face.ToString()) Then
item.thumbnail_base64 = BaseViewModel.ConvertBitmapToBase64(My.Resources.gender_unknown_2)
item.thumbnail_bitmap = My.Resources.gender_unknown_2
ElseIf item.system_type.Equals(EnumType.SystemType.people.ToString()) Then
item.thumbnail_base64 = BaseViewModel.ConvertBitmapToBase64(My.Resources.People)
item.thumbnail_bitmap = My.Resources.People
End If
End If
Dim tmpDate As DateTime
Dim shotDate As Date
If DateTime.TryParseExact(item.shot_date_time, RESPONSE_DATE_FORMAT2, Nothing, DateTimeStyles.AssumeLocal, tmpDate) Then
shotDate = tmpDate
Else
shotDate = DateTime.Now
End If
Dim dateKey As String = shotDate.ToString(PRIVATE_DATE_FORMAT)
If Not dataDic.ContainsKey(dateKey) Then
Dim thumbList = New ObservableCollection(Of Object)
Dim objThumb As Object = MappingVIThumbnailFromResponse(item, shotDate)
thumbList.Add(objThumb)
dataDic.Add(dateKey, thumbList)
Else
Dim objThumb As Object = MappingVIThumbnailFromResponse(item, shotDate)
dataDic.Item(dateKey).Add(objThumb)
End If
Catch ex As Exception
Dim b As Integer = 0
End Try
Next
Catch ex As Exception
Dim c As Integer = 0
End Try
End Sub
After, I binding data as below
Dim result As ObservableCollection(Of ListViewThumbnailViewModel) = New ObservableCollection(Of ListViewThumbnailViewModel)
If dataDic.Count > 0 Then
If token.IsCancellationRequested Then Return data
For Each pair As KeyValuePair(Of String, ObservableCollection(Of Object)) In dataDic
Dim _date As DateTime = DateTime.ParseExact(pair.Key, PRIVATE_DATE_FORMAT, CultureInfo.InvariantCulture)
result.Add(New ListViewThumbnailViewModel() With {.DateItem = _date, .ListThumbnail = pair.Value})
_viewModel.ResultSearch.TotalData += pair.Value.Count
Next
_viewModel.ResultSearch.ListResult = result
_viewModel.ResultSearch.ListResultActual = result
_viewModel.ResultSearch.PageSize = PageHelper.GetPageSizeWithZoom(_viewModel.ResultSearch.ZoomImage * 10, _viewModel.ResultSearch.PageSizeStart, _viewModel.ResultSearch.NumberChange)
_viewModel.ResultSearch.PageCurrent = 0
_viewModel.ResultSearch.TotalPage = PageHelper.GetTotalPageByPageSize(result.Count, _viewModel.ResultSearch.PageSize)
Else
_viewModel.ResultSearch.ListResult = Nothing
_viewModel.ResultSearch.ListResultActual = Nothing
End If
Catch ex As Exception
Throw New AIMatchingException(ex)
End Try
Return data
What should I do? please help me, thanks!!!