quickly load text to excel - vb.net

Question

I'm trying to load a CSV or TSV into Excel, and for small files it works great; small files being < 5kb. The problem is that when I attempt to load larger files into Excel the process can take a long time. The files that I need the app to load can contain anywhere from 5 - 100 columns with anywhere from 5 to 20,000 rows.
I have tried using the BackgroundWorker, Threadpools, Parallel.For, Parallel.ForEach, but they all seem to have the same performance for this task.
The app itself is designed to take a list of headers from a separate text file, then load it into Excel, apply formatting, then loads the actual CSV/TSV file into Excel.
Here's what I have so far, this sub gets kicked off by the background worker:
Private Sub LoadTextFile(ByVal xlApp As Excel.Application, ByVal xlWb As Excel.Workbook, ByVal xlWs As Excel.Worksheet, ByVal xlRange As Excel.Range)
Dim SheetName As String = "Sheet1"
If xlWs Is Nothing Then
xlWs = DirectCast(xlWb.Sheets.Add(After:=xlWb.Sheets(xlWb.Sheets.Count), Count:=1, Type:=Excel.XlSheetType.xlWorksheet), Excel.Worksheet)
End If
'Read lines and store in a string array
Dim lines() As String = File.ReadAllLines(FileToLoad)
'Parse and write lines to Excel
For i As Integer = 0 To lines.Length - 1
'Set new row range
xlRange = xlWs.Range(startCol + (i + 2).ToString + ":" + endCol + (i + 2).ToString)
'Parse the line to load
Dim lineDetail() As String = lines(i).Split(fileDelimiter)
'Load into Excel
xlRange.Value = lineDetail
Next
End Sub
Here are some performance times:
89 Columns - 2,000 rows: Average Load Time = 7 sec.
89 Columns - 4,000 rows: Average Load Time = 12 sec.
91 Columns - 10,000 rows: Average Load Time = 28 sec.
91 Columns - 24,000 rows: Average Load Time = 70 sec.
107Columns - 8,732 rows: Average Load Time = 17 sec.
I keep thinking, "How does Excel load these files almost instantly?!?" Anyways, I will be super grateful to anyone that can help me optimize this so getting the data into Excel doesn't take so long. Thank you in advance.

Answer 1

This is what I came up with and I think it works very well. Thanks to TnTinMn for pointing me in the right direction :)
Dim xlApp As New Excel.Application
Dim xlWb As Excel.Workbook
Dim xlWs As Excel.Worksheet
Dim xlRange As Excel.Range
'Start Excel and Create Application Object
xlApp = CreateObject("Excel.Application")
'Set invisible until all loading is completed
xlApp.Visible = False
'Get/Set references of active workbook/sheet
xlWb = xlApp.Workbooks.Add
xlWb = xlApp.ActiveWorkbook
xlWs = xlWb.ActiveSheet
xlRange = xlWs.Range("$A$1")
'Used to specify the data type for each column. 2 = Text
Dim array = New Object() {2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, _
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2 _
, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, _
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2}
'TextFilePlatform ANSI: 1252
With xlWs.QueryTables.Add(Connection:="TEXT;" + cfg.filePath, Destination:=xlRange)
.Name = "sec"
.FieldNames = True
.RowNumbers = False
.FillAdjacentFormulas = False
.PreserveFormatting = True
.RefreshOnFileOpen = False
.RefreshStyle = Excel.XlCellInsertionMode.xlInsertDeleteCells
.SavePassword = False
.SaveData = True
.AdjustColumnWidth = True
.RefreshPeriod = 0
.TextFilePromptOnRefresh = False
.TextFilePlatform = 1252
.TextFileStartRow = 1
.TextFileParseType = Excel.XlTextParsingType.xlDelimited
.TextFileTextQualifier = Excel.XlTextQualifier.xlTextQualifierDoubleQuote
.TextFileConsecutiveDelimiter = False
.TextFileTabDelimiter = cfg.fileTSV
.TextFileSemicolonDelimiter = False
.TextFileCommaDelimiter = cfg.fileCSV
.TextFileSpaceDelimiter = False
.TextFileColumnDataTypes = array
.TextFileTrailingMinusNumbers = True
.Refresh(BackgroundQuery:=False)
End With
'Add headers do formatting here
'<Additional Worksheet formats here>
xlApp.Visible = True