查询值的数量和目的地字段的数量不同

这是自动存储值到 TotalAmt_tx.Text 的函数。

   void TotalAmount()
            {
                .
                .
                .
                .
                TotalAmt_tx.Text = Total.ToString("00.00");
                .
                .
                .
                catch { }
            }

保存按钮代码：这里是我的表单图像

private void Save_bt_Click(object sender, EventArgs e)
        {
            //Purchase Table
            {
                string insertPur = "Insert into Purchase (Invoice,VendorName,PurchaseDate,TotalAmt) values ("+Invoice_tx.Text+"," +
                    "'"+VendorName_cb.Text+"','"+PurchaseDate_dt.Value.Date.ToString()+"',"+TotalAmt_tx.Text+" )";

                OleDbDataAdapter da = new OleDbDataAdapter(insertPur, conn);
                DataSet ds = new DataSet();
                da.Fill(ds);                
            }

            //Purchase Item Table
            for (int i = 0; i < metroGrid1.Rows.Count; i++)
            {
                string insertPur = "Insert into PurchaseItem (Invoice, PId, Product, Qty, Rate, Amount) values (" + Invoice_tx.Text + "," +
                    ""+metroGrid1.Rows[i].Cells["PId"].Value.ToString()+ ",'" + metroGrid1.Rows[i].Cells["Product"].Value.ToString() + "'," +
                    "" + metroGrid1.Rows[i].Cells["Qty"].Value.ToString() + "," + metroGrid1.Rows[i].Cells["Rate"].Value.ToString() + "," +
                    "" + metroGrid1.Rows[i].Cells["Amount"].Value.ToString() + ")";

                OleDbDataAdapter da = new OleDbDataAdapter(insertPur, conn);
                DataSet ds = new DataSet();
                da.Fill(ds);
            }
            MessageBox.Show("Data Saved!!");

出现问题是因为这个

TotalAmt_tx.Text = Total.ToString("00.00")

我该怎么办，解决它？？我尝试遵循一些有关格式化字符串的教程，但没有任何效果。请帮忙