Option Strict On
Option Explicit On
Option Infer Off

Imports System.IO.Path

Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, _
                           ByVal e As System.EventArgs) _
                           Handles MyBase.Load

        Dim desktop As String = _
            Environment.GetFolderPath(Environment.SpecialFolder.Desktop)

        Dim textFilePath As String = _
            Combine(desktop, "ExampleTextFile.txt")

        Dim blankLines() As Integer = GetBlankLines(textFilePath)

        Stop

    End Sub

    Private Function GetBlankLines(ByVal textFilePath As String) As Integer()

        Dim retVal() As Integer = New Integer() {}

        If Not String.IsNullOrWhiteSpace(textFilePath) Then
            If IO.File.Exists(textFilePath) Then
                Dim lineNumber As Integer = 1
                Dim tempList As New List(Of Integer)

                Using rdr As New System.IO.StreamReader(textFilePath)
                    Do While rdr.Peek() >= 0
                        Dim itm As String = rdr.ReadLine.Trim

                        If String.IsNullOrWhiteSpace(itm) Then
                            tempList.Add(lineNumber)
                        End If

                        lineNumber += 1
                    Loop
                End Using

                If tempList.Count > 0 Then
                    retVal = tempList.ToArray
                End If
            End If
        End If

        Return retVal

    End Function
End Class