Public Class Form1

    Private Sub SaveGridDataInFile(ByRef fName As String)

        Try
            Dim objWriter As New System.IO.StreamWriter(fName, True)

            For iRow As Integer = 0 To Me.DataGridView1.RowCount - 1
                objWriter.WriteLine(Me.DataGridView1.Item(0, iRow).Value & ";")
            Next
            objWriter.Close()
            MsgBox("Text written to file")
        Catch e As Exception
            MessageBox.Show("Error occured while writing to the file." + e.ToString())
        Finally
            FileClose(1)
        End Try

    End Sub

    Private Sub PopulateDataGridView()

        DataGridView1.ColumnCount = 2

        With DataGridView1
            .Columns(0).Name = "Number"
            .Columns(1).Name = "Item"
        End With

        For iRow As Integer = 0 To 236000 - 1
            Dim row0 As String() = {iRow, "Item: " & iRow}
            Me.DataGridView1.Rows.Add(row0)
        Next

    End Sub
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        PopulateDataGridView()
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        SaveGridDataInFile("C:\exportDGV.csv")
    End Sub
End Class