Datatable和Datagridview以及访问值的方法

Question

我正在尝试将数据作为DataTable的形式推送到函数中，而在另一种形式上，我有一个DataGridView，其中包含该函数所必需的数据。

我有DataGridView invoice_data;，我试过This Link 如下，

DataTable id = (DataTable)(invoice_data.DataSource);

现在网格表总共有0-6列。

现在这个功能，

        public static string VPfn_GenInvoicePdf(string[] ivdata, DataTable ida)
    {
        StringBuilder sb = new StringBuilder();

        try
        {
            using (System.IO.StreamReader Reader = new System.IO.StreamReader("inv.tpl"))
            {
                StringBuilder Sb = new StringBuilder();
                string fileContent = Reader.ReadToEnd();
                sb.Append(fileContent);
                sb.AppendLine("<h2 class='name'>"+ VPfunctions.VPfn_N2ID_customer(ivdata[1]) +"</h2>");
                sb.AppendLine("<div class='address'>"+ VPfunctions.VPfn_CusAddr(Int16.Parse(ivdata[1]))+"</div>");
                sb.AppendLine("<div class='email'><a href='mailto:"+ VPfunctions.VPfn_CusEmail(Int16.Parse(ivdata[1]))+ "'>"+ VPfunctions.VPfn_CusEmail(Int16.Parse(ivdata[1])) + "</a></div>");
                sb.AppendLine("</div> < div id = 'invoice' >");
                sb.AppendLine("<h1>INVOICE"+ivdata[0]+"</h1>");
                sb.AppendLine("<div class='date'>Date of Invoice:"+DateTime.Today+"</div>");
                sb.AppendLine("<div class='date'>Due Date:"+ DateTime.Today.AddDays(30)+"</div>");
                sb.AppendLine("</div></ div >< table border = '0' cellspacing = '0' cellpadding = '0' >< thead >< tr > ");
                sb.AppendLine("<th class='no'>#</th><th class='desc'>DESCRIPTION</th><th class='unit'>UNIT PRICE</th><th class='qty'>QUANTITY</th><th class='vat'>VAT</th><th class='total'>TOTAL</th></tr></thead><tbody>");


                foreach(DataGridViewRow x in ida.Rows)
                {
                    sb.AppendLine("<tr>");
                    sb.AppendLine("<td class='no'>"+x.Cells[0].ToString()+"</td>");
                    sb.AppendLine("<td class='desc'><h3>"+x.Cells[1].ToString()+"</h3></td>");
                    sb.AppendLine("<td class='unit'>₹"+x.Cells[2].ToString()+"</td>");
                    sb.AppendLine("<td class='qty'>"+x.Cells[3].ToString()+"</td>");
                    sb.AppendLine("<td class='vat>"+x.Cells[5].ToString()+"%</td>");
                    sb.AppendLine("<td class='total'>₹"+x.Cells[6].ToString()+"</td>");
                    sb.AppendLine("</tr>");
                } 


                sb.AppendLine("</tbody><tfoot><tr>");
                sb.AppendLine("<td colspan='3'></td>< td colspan = '2' > SUBTOTAL </ td >< td >₹"+ ivdata[4].ToString()+ "</ td ></ tr ><tr> ");
                sb.AppendLine("<td colspan='3'></td><td colspan='2'>TAX (4+1%)</td><td>+ ₹"+ivdata[5].ToString()+"</td></tr><tr>");
                sb.AppendLine("<td colspan='3'></td><td colspan='2'>DISCOUNT (10%)</td><td>- ₹"+ivdata[6].ToString()+"</td></tr><tr>");
                sb.AppendLine("<td colspan='3'></td><td colspan='2'>GRAND TOTAL</td><td>₹"+ivdata[7].ToString()+"</td></tr></tfoot></table>");
                sb.AppendLine("<div id='thanks'>Thank you!</div><div id='notices'><div>NOTICE:</div><div class='notice'>A finance charge of 1.5% will be made on unpaid balances after 30 days.</div></div></main><footer>Invoice was created on a computer and is valid without the signature and seal.</footer></body></html>");

                return sb.ToString();
            }
        }
        catch(Exception ex)
        {
            MessageBox.Show("Invoice template loading failed! Please run updater! "+ex.Message);
            return null;
        }

这会以html格式创建发票，以便我可以轻松转换为pdf格式。

现在，出于测试目的，我运行了以下代码，我得到的索引超出范围错误。

private void button1_Click(object sender, EventArgs e)
{
    string[] idata = new string[8];
    idata[0] = tid.Text;
    idata[1] = tcid.Text;
    idata[2] = DateTime.Now.ToString();
    idata[3] = null;
    idata[4] = tst.Text;
    idata[5] = tat.Text;
    idata[6] = tdis.Text;
    idata[7] = ttotal.Text;

    DataTable id = (DataTable)(invoice_data.DataSource);
    string invdata = VPInvoice.VPfn_GenInvoicePdf(idata, id);
    webBrowser1.DocumentText = invdata;

}

错误：来自该捕获异常：对象引用未设置为对象的实例