How to export certain column from datagridview to excel

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C#

DataGridView

Hello everyone. My name is Oktavianus Misro Adrianto.
Pardon me if I ask a very basic question, but I am new to this.

I have a Datagridview which contain students information fromm sql server database. now I want to export the data to an excel file. the file was succesfully exported, but what I am trying to do is exporting certain columns or maybe when user click the export button, an option form appear in which the user can choose which column they want to export.

anyone has an idea about how to do this?

What I have tried:

Here is my code

private void btnExcel_Click(object sender, EventArgs e)
       {
           Cursor.Current = Cursors.WaitCursor;
           {
               try
               {
                   Microsoft.Office.Interop.Excel._Application app = new Microsoft.Office.Interop.Excel.Application();
                   Microsoft.Office.Interop.Excel._Workbook workbook = app.Workbooks.Add(Type.Missing);
                   Microsoft.Office.Interop.Excel._Worksheet worksheet = null;
                   app.Visible = true;
                   worksheet = workbook.Sheets["Sheet1"];
                   worksheet = workbook.ActiveSheet;
                   worksheet.Name = "Database Siswa";
                   //lokasi untuk menyimpan file Excel
                   SaveFileDialog saveDialog = new SaveFileDialog
                   {
                       Filter = "Excel files (*.xlsx)|*.xlsx|All files (*.*)|*.*",
                       FilterIndex = 2
                   };

                   if (saveDialog.ShowDialog() == System.Windows.Forms.DialogResult.OK)
                   {
                       workbook.SaveAs(saveDialog.FileName);
                       MessageBox.Show("Data telah berhasil dieksport", "Success", MessageBoxButtons.OK, MessageBoxIcon.Information);
                   }
                   try
                   {
                       for (int i = 0; i < dataGridViewSiswa.Columns.Count; i++)
                       {
                           worksheet.Cells[1, i + 1] = dataGridViewSiswa.Columns[i].HeaderText;
                       }
                       for (int i = 0; i < dataGridViewSiswa.Rows.Count; i++)
                       {
                           for (int j = 0; j < dataGridViewSiswa.Columns.Count; j++)
                           {
                               //milih kolom mana yang mau dieksport
                               if (dataGridViewSiswa.Rows[i].Cells[j].Value != null)
                               {
                                   worksheet.Cells[i + 2, j + 1] = dataGridViewSiswa.Rows[i].Cells[j].FormattedValue.ToString();
                               }
                               else
                               {
                                   worksheet.Cells[i + 2, j + 1] = "";
                               }
                           }
                       }
                   }
                   catch (System.Exception ex)
                   {
                       MessageBox.Show(ex.Message);
                   }

                   finally
                   {
                       app.Quit();
                       workbook = null;
                       worksheet = null;
                   }
               }
               catch (Exception ex) { MessageBox.Show(ex.Message.ToString()); }
           }
       }