Exporting data from datagrid view to excel

i've made a small tool that searches an access DB in back end & dumps the results in a Datagridview, now i want to export those results to excel, after googling i found a code that does it for me , it's working partially for me. It writes the Headers to a new excel file but then for some reason i getting below error (on the blue line in code):

Conversion from type 'DBNull' to type 'String' is not valid.

Code:

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Private Sub btnExport_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExport.Click

        Dim objExcel As New Microsoft.Office.Interop.Excel.Application
        Dim oXL As New Microsoft.Office.Interop.Excel.Application
        Dim oWB As Microsoft.Office.Interop.Excel.Workbook
        Dim oSheet As Microsoft.Office.Interop.Excel.Worksheet
        Dim oRng As Microsoft.Office.Interop.Excel.Range

        'oXL = CType(CreateObject("Excel.Application"), a)
        oXL.Visible = True

        ' Get a new workbook.
        oWB = oXL.Workbooks.Add
        oSheet = CType(oWB.ActiveSheet, Worksheet)

        ' Add table headers going cell by cell.
        For Each cols As DataGridViewColumn In Me.DataGridView1.Columns
            oSheet.Cells.Columns.CurrentRegion.Columns(cols.Index + 1) = cols.HeaderText
        Next

        ' Format A1:D1 as bold, vertical alignment = center.
        With oSheet.Range("A1", "Z1")
            .Font.Bold = True
            .VerticalAlignment = Microsoft.Office.Interop.Excel.XlVAlign.xlVAlignCenter
        End With

        ' Create an array to set multiple values at once.
        Dim rowcount As Integer = Me.DataGridView1.Rows.Count
        Dim colcount As Integer = Me.DataGridView1.Columns.Count
        Dim GridData(rowcount, colcount) As String

        For Each row As DataGridViewRow In Me.DataGridView1.Rows
            Dim rowindex As Integer = row.Index
            For Each cells As DataGridViewCell In row.Cells
                Dim cellindex As String = cells.ColumnIndex
                GridData(rowindex, cellindex) = CStr(cells.Value)
            Next
        Next


        ' Fill A2:B6 with an array of values (First and Last Names).
        oSheet.Range("A2", "G" & Me.DataGridView1.Rows.Count).Value = GridData

        ' Fill C2:C6 with a relative formula (=A2 & " " & B2). if you want to add a formula
        oRng = oSheet.Range("C2", "C6")
        oRng.Formula = "=A2 & "" "" & B2"

        ' Fill D2:D6 with a formula(=RAND()*100000) and apply format.if you want to apply a format
        oRng = oSheet.Range("D2", "D6")
        oRng.Formula = "=RAND()*100000"
        oRng.NumberFormat = "$0.00"

        ' AutoFit columns A:D.
        oRng = oSheet.Range("A1", "Z1")
        oRng.EntireColumn.AutoFit()

        ' Make sure Excel is visible and give the user control
        ' of Excel's lifetime.
        oXL.Visible = True
        oXL.UserControl = True

        ' Make sure that you release object references.
        oRng = Nothing
        oSheet = Nothing
        oWB = Nothing
        oXL.Quit()
        oXL = Nothing

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pls help ?

vb Code:

Dim cellindex As String = cells.ColumnIndex
                GridData(rowindex, cellindex) = CStr(cells.Value)

Try :

vb Code:

Dim cellindex As Integer = cells.ColumnIndex

Justin

no luck :(

still the same error