Error while trying to export DataGridView as pdf - vb.net

Question

I'm trying to export a populated datagridview with the following code:
Imports System.Data.OleDb
Imports Microsoft.Office.Interop.Excel
Imports System.Drawing
Imports DGVPrinterHelper
Imports iTextSharp
Imports iTextSharp.text.pdf
Imports iTextSharp.text
Imports System.Data.Odbc
Imports System.IO
Private Sub Export_Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
SaveFileDialog1.ShowDialog()
If SaveFileDialog1.FileName = "" Then
MsgBox("Enter Filename to create PDF")
Exit Sub
Else
ExportDataToPDFTable()
MsgBox("PDF Created Successfully")
End If
End Sub
Private Function GetDataTable() As DataTable
Dim dataTable As New Data.DataTable("MyDataTable")
'Create another DataColumn Name
For column As Integer = 1 To DataGridView1.ColumnCount - 1
Dim dataColumn_1 As New DataColumn(DataGridView1.Columns(column).HeaderText.ToString(), GetType(String))
dataTable.Columns.Add(dataColumn_1)
'Now Add some row to newly created dataTable
Dim dataRow As DataRow
For i As Integer = 0 To DataGridView1.Rows.Count - 1
dataRow = dataTable.NewRow()
' Important you have create New row
dataRow(DataGridView1.Columns(column).HeaderText.ToString()) = DataGridView1.Rows(i).Cells(column).Value.ToString()
dataTable.Rows.Add(dataRow)
Next i
Next column
dataTable.AcceptChanges()
Return dataTable
End Function
Private Sub ExportDataToPDFTable()
Dim paragraph As New Paragraph
Dim doc As New Document(iTextSharp.text.PageSize.A4, 40, 40, 40, 10)
Dim wri As PdfWriter = PdfWriter.GetInstance(doc, New FileStream(SaveFileDialog1.FileName + ".pdf", FileMode.Create))
doc.Open()
Dim font12BoldRed As New iTextSharp.text.Font(iTextSharp.text.Font.FontFamily.TIMES_ROMAN, 12.0F, iTextSharp.text.Font.UNDERLINE Or iTextSharp.text.Font.BOLDITALIC, BaseColor.RED)
Dim font12Bold As New iTextSharp.text.Font(iTextSharp.text.Font.FontFamily.TIMES_ROMAN, 12.0F, iTextSharp.text.Font.BOLD, BaseColor.BLACK)
Dim font12Normal As New iTextSharp.text.Font(iTextSharp.text.Font.FontFamily.TIMES_ROMAN, 12.0F, iTextSharp.text.Font.NORMAL, BaseColor.BLACK)
Dim p1 As New Phrase
p1 = New Phrase(New Chunk("PDF From Datagridview Data", font12BoldRed))
doc.Add(p1)
'Create instance of the pdf table and set the number of column in that table
Dim PdfTable As New PdfPTable(5)
PdfTable.TotalWidth = 490.0F
'fix the absolute width of the table
PdfTable.LockedWidth = True
'relative col widths in proportions - 1,4,1,1 and 1
Dim widths As Single() = New Single() {1.0F, 4.0F, 1.0F, 1.0F, 1.0F}
PdfTable.SetWidths(widths)
PdfTable.HorizontalAlignment = 1 ' 0 --> Left, 1 --> Center, 2 --> Right
PdfTable.SpacingBefore = 2.0F
'pdfCell Decleration
Dim PdfPCell As PdfPCell = Nothing
'Assigning values to each cell as phrases
PdfPCell = New PdfPCell(New Phrase(New Chunk("Taxcode", font12Bold)))
'Alignment of phrase in the pdfcell
PdfPCell.HorizontalAlignment = PdfPCell.ALIGN_CENTER
'Add pdfcell in pdftable
PdfTable.AddCell(PdfPCell)
PdfPCell = New PdfPCell(New Phrase(New Chunk("Tax Name", font12Bold)))
PdfPCell.HorizontalAlignment = PdfPCell.ALIGN_CENTER
PdfTable.AddCell(PdfPCell)
PdfPCell = New PdfPCell(New Phrase(New Chunk("Cess Tax", font12Bold)))
PdfPCell.HorizontalAlignment = PdfPCell.ALIGN_CENTER
PdfTable.AddCell(PdfPCell)
PdfPCell = New PdfPCell(New Phrase(New Chunk("Sales Tax", font12Bold)))
PdfPCell.HorizontalAlignment = PdfPCell.ALIGN_CENTER
PdfTable.AddCell(PdfPCell)
PdfPCell = New PdfPCell(New Phrase(New Chunk("Other Tax", font12Bold)))
PdfPCell.HorizontalAlignment = PdfPCell.ALIGN_CENTER
PdfTable.AddCell(PdfPCell)
Dim dt As DataTable = GetDataTable()
If dt IsNot Nothing Then
'Now add the data from datatable to pdf table
For rows As Integer = 0 To dt.Rows.Count - 1
For column As Integer = 0 To dt.Columns.Count - 1
PdfPCell = New PdfPCell(New Phrase(dt.Rows(rows)(column).ToString(), font12Normal))
If column = 0 Or column = 1 Then
PdfPCell.HorizontalAlignment = PdfPCell.ALIGN_LEFT
Else
PdfPCell.HorizontalAlignment = PdfPCell.ALIGN_RIGHT
End If
PdfTable.AddCell(PdfPCell)
Next
Next
'Adding pdftable to the pdfdocument
doc.Add(PdfTable)
End If
doc.Close()
End Sub
When I run the program a click the button it prompts me with the SaveFileDialog, but once I click save I get the error "Unable to cast object of type 'System.Data.DataTable' to type 'Microsoft.Office.Interop.Excel.DataTable'." at the "Return dataTable" line in the Private Function GetDataTable(). Can anyone help me resolve this issue? And please feel free to point out other errors with my code (if there are any)