How do I assign a single row datatable value as variable and use it in arithmetic function? C# , SQLEXPRESS

See more:

C#

SQL

SQLEXPRESS

sorry im bad at coding but i need this,

well..
in my table called Products
got 2 column there is Product and Price
in Price column contains a decimal value 1000

can i get that value(1000) to be a variable so i can use it into arithmetic function?
and it seems to connect the database to my form is incorrect as well,

pls modify all my source! and what i need to add! thanks
I would appreciate any help!

What I have tried:

This's the DataAccessLayer
DataAccess.cs

namespace CS_Sistem_Managemen_Restoran
{
    class DataAccess
    {
        public SqlConnection con;

        public void Connection(string spName = null)
        {
            string strConnect = "Server=PC\\SQLEXPRESS;Database=MyLoginApp;Trusted_Connection=True;";
            SqlConnection conn = new SqlConnection();
            SqlConnection dt = new SqlConnection();
            

            try
            {
                //Connect to the database
                conn = new SqlConnection(strConnect);
                conn.Open();



                //Execute command
                SqlCommand cmd = new SqlCommand(spName, conn);
                SqlCommand command = conn.CreateCommand();
                SqlDataReader dr = cmd.ExecuteReader();

                


            }
            catch (Exception ex)
            {
                throw ex;
            }
        }
         
    }
}

Form1.cs BtnHitung

 private void btnHitung_Click(object sender, EventArgs e)
        {
            DataAccess conss = new DataAccess();
            conss.Connection();
            DataTable dt = new DataTable("Products");

            //declare
            Double BasoSUCost = Convert.ToInt32(dt.Rows[1]["price"].ToString());
	    Double ItemBasoSU;
	    Double TotalBasoSU;


if (int.TryParse(txtBasoSU.Text, out NumberofOrder))
            {
                ItemBasoSU = Double.Parse(txtBasoSU.Text);
                TotalBasoSU = BasoSUCost * ItemBasoSU;
		
		txtTotal.Text = String.Format("Rp. {0:N} ", TotalBasoSU);
	    }
	}