codes to calculate Vat snd Stamp duty

Question

Please i needs codes to calculate 5% Vat and 1% stamp duty on every transaction in my sales invoice.

 

your kind gesture will be appreciated.

Thank you

 

 

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;
namespace NSPM_Sales_Invoice
{
 public partial class frmNewBill: Form
 {
  SqlConnection con = new SqlConnection(Properties.Settings.Default.NSPM_Sales_InvoiceCon);
  SqlCommand cmd;
  public frmNewBill()
  {
   InitializeComponent();
   txtDeleteUpdate.Visible = false;
  }
  private void textBox1_TextChanged(object sender, EventArgs e)
  {
  }
  private void panel1_Paint(object sender, PaintEventArgs e)
  {
  }
  private void tableLayoutPanel1_Paint(object sender, PaintEventArgs e)
  {
  }
  private void frmNewBill_Load(object sender, EventArgs e)
  {
   cmbDescription.Items.Clear();
   con.Open();
   cmd = con.CreateCommand();
   cmd.CommandType = CommandType.Text;
   cmd.CommandText = "Select ProName from tbl_Products order by ProName asc";
   cmd.ExecuteNonQuery();
   DataTable dt = new DataTable();
   SqlDataAdapter da = new SqlDataAdapter(cmd);
   da.Fill(dt);
   foreach(DataRow dr in dt.Rows)
   {
    cmbDescription.Items.Add(dr["ProName"].ToString());
   }
   con.Close();
   dataGridView1.Columns[5].Visible = false;
   dataGridView1.Columns[6].Visible = false;
  }
  private void btnAdd_Click(object sender, EventArgs e)
  {
   if (cmbDescription.Text == "")
   {
    MessageBox.Show("Description is Empty");
   } else if (txtQuantity.Text == "")
   {
    MessageBox.Show("Quantity is Empty");
   } else if (txtUnitPrice.Text == "")
   {
    MessageBox.Show("Unit Price is Empty");
   } else if (txtJobNo.Text == "")
   {
    MessageBox.Show("JobNo is Empty");
    if (txtDeleteUpdate.Text == "")
    {
     int row = 0;
     dataGridView1.Rows.Add();
     row = dataGridView1.Rows.Count - 1;
     dataGridView1["Description", row].Value = cmbDescription.Text;
     dataGridView1["Quantity", row].Value = txtQuantity.Text;
     dataGridView1["UnitPrice", row].Value = txtUnitPrice.Text;
     dataGridView1["GoodValue", row].Value = txtGoodValue.Text;
     dataGridView1["JobNo", row].Value = txtJobNo.Text;
     dataGridView1["Date", row].Value = dateTimePicker1.Value.ToString("dd-MM-yyyy");
     dataGridView1.Refresh();
     cmbDescription.Focus();
     if (dataGridView1.Rows.Count > 0)
     {
      dataGridView1.CurrentCell = dataGridView1.Rows[dataGridView1.Rows.Count - 1].Cells[1];
     }
    } else
    {
     btnAdd.Text = "UPDATE";
     int i = 0;
     DataGridViewRow row = dataGridView1.Rows[i];
     row.Cells[1].Value = cmbDescription.Text;
     row.Cells[2].Value = txtQuantity.Text;
     row.Cells[3].Value = txtUnitPrice.Text;
     row.Cells[4].Value = txtGoodValue.Text;
     row.Cells[5].Value = txtJobNo.Text;
     btnAdd.Text = "ADD";
    }
    cleartextbox();
    gridGoodValue();
   }
  }
  private void dataGridView1_RowPostPaint(object sender, DataGridViewRowPostPaintEventArgs e)
  {
   this.dataGridView1.Rows[e.RowIndex].Cells[0].Value = (e.RowIndex + 1).ToString();
  }
  int i;
  private void dataGridView1_CellDoubleClick(object sender, DataGridViewCellEventArgs e)
  {
   i = e.RowIndex;
   DataGridViewRow row = dataGridView1.Rows[i];
   cmbDescription.Text = row.Cells[1].Value.ToString();
   txtQuantity.Text = row.Cells[2].Value.ToString();
   txtUnitPrice.Text = row.Cells[3].Value.ToString();
   txtGoodValue.Text = row.Cells[4].Value.ToString();
   txtDeleteUpdate.Text = row.Cells[0].Value.ToString();
   btnAdd.Text = "UPDATE";
  }
  private void btnDelete_Click(object sender, EventArgs e)
  {
   if (txtDeleteUpdate.Text == "")
   {
    MessageBox.Show("Select Product to Delete");
   } else
   {
    foreach(DataGridViewRow row in dataGridView1.SelectedRows)
    {
     if (!row.IsNewRow) dataGridView1.Rows.Remove(row);
    }
   }
   btnAdd.Text = "ADD";
   gridGoodValue();
   cleartextbox();
  }
  public void cleartextbox()
  {
   cmbDescription.Text = "";
   txtQuantity.Text = "";
   txtUnitPrice.Text = "";
   txtGoodValue.Text = "";
   txtJobNo.Text = "";
   txtDeleteUpdate.Text = "";
  }
  public void CalGoodValue()
  {
   double a1, b1, i;
   double.TryParse(txtUnitPrice.Text, out a1);
   double.TryParse(txtQuantity.Text, out b1);
   i = a1 * b1;
   if (1 > 0)
   {
    txtGoodValue.Text = i.ToString("C").Remove(0, 1);
   }
  }
  private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
  {
  }
  private void txtQuantity_Leave(object sender, EventArgs e)
  {
   CalGoodValue();
  }
  private void txtQuantity_TextChanged(object sender, EventArgs e)
  {
  }
  private void txtUnitPrice_Leave(object sender, EventArgs e)
  {
   CalGoodValue();
  }
  public void gridGoodValue()
  {
   double sum = 0;
   for (int i = 0; i < dataGridView1.Rows.Count; ++i)
   {
    sum += Convert.ToDouble(dataGridView1.Rows[i].Cells[4].Value);
   }
   txtTotalGoodValue.Text = sum.ToString();
  }
  {
  }
  {
  }
 }
}