Problem in looping.undesired rows of the datagridview are being exported to excel

Please edit the code because I am unable to export the selected rows of DataGridView to Excel based on Checkbox selection .The below code export all the rows even those rows are not selected(checked) by the user.

What I have tried:

public void exportSelectedRowsToExcel()        {
            // creating Excel Application  
            Microsoft.Office.Interop.Excel._Application app = new Microsoft.Office.Interop.Excel.Application();
            // creating new WorkBook within Excel application  
            Microsoft.Office.Interop.Excel._Workbook workbook = app.Workbooks.Add(Type.Missing);
            // creating new Excelsheet in workbook  
            Microsoft.Office.Interop.Excel._Worksheet worksheet = null;
            // see the excel sheet behind the program  
            app.Visible = true;
            // get the reference of first sheet. By default its name is Sheet1.  
            // store its reference to worksheet  
            worksheet = workbook.Sheets["Sheet1"];
            worksheet = workbook.ActiveSheet;
            // changing the name of active sheet  
            worksheet.Name = DateTime.Now.ToString("yyyyMMddHHmmssfff");

                

            // storing header part in Excel  
            for (int i = 1; i < CategoryGV.Columns.Count + 1; i++)
            {
                worksheet.Cells[1, i] = CategoryGV.Columns[i - 1].HeaderText;
            }

            // storing Each row and column value to excel sheet  
            for (int i = 0; i < CategoryGV.Rows.Count - 1; i++)
            {
                for (int j = 0; j < CategoryGV.Columns.Count; j++)
                {
                    worksheet.Cells[i + 2, j + 1] = Convert.ToString(CategoryGV.Rows[i].Cells[j].Value);
                }
            }


            // save the application 
            workbook.SaveAs(Environment.GetFolderPath(Environment.SpecialFolder.Desktop) + 
                 "\\ExportedCategory.xls", Type.Missing, Type.Missing, Type.Missing, Type.Missing, 
                  Type.Missing,Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlExclusive, Type.Missing, 
                  Type.Missing, Type.Missing, Type.Missing);
            // Exit from the application  
            app.Quit();
        }

private void btnExportToExcel_Click(object sender, EventArgs e)
        {
            DataGridViewRow row = new DataGridViewRow();

            for (int i = 0; i < CategoryGV.Rows.Count; i++)
            {
                row = CategoryGV.Rows[i];
                if (Convert.ToBoolean(row.Cells["chkBox"].Value))
                {
                    int id = Convert.ToInt16(row.Cells["id"].Value);
                    exportSelectedRowsToExcel();
                    i--;
                }

            }

Tags: SQL, C# 5.0, .NET, Windows Forms, DataGridView