How to insert data by using store procedure in three tier architecture?

See more:

C#

ASP.NET

I am developing simple student management system using ASP .Net by using 3 tier architecture. I have placed my data layer in db_connection.cs file under APP Code folder along with other class files those are acting as the business logic layer.

the code of db_connection.cs is

public class db_connection
{
    public SqlConnection con;
    public SqlDataAdapter adp;
    public DataSet ds = new DataSet();
    public SqlCommand cmd;

	public db_connection()
	{
		
	}

    public void connection()
    {
        con = new SqlConnection(ConfigurationManager.ConnectionStrings["ds"].ConnectionString);
        con.Open();
    }
 

    public int inupdel(string sql)
    {
        connection();
        cmd = new SqlCommand();
        return cmd.ExecuteNonQuery();

    }
}


And the students_details.cs file code --

public class student_details
{
    db_connection db = new db_connection();
	public student_details()
	{
    }


    public int insert(string name, string address, string city, string state, int pin, int dept_id, DateTime doa, int coursefee)
    {
       
            db.cmd = new SqlCommand("spCreateStudentDetails");
        db.cmd.CommandType = CommandType.StoredProcedure;
         
        db.cmd.Parameters.AddWithValue("@StudentName", name);
        db.cmd.Parameters.AddWithValue("@StudentAddress", address);
        db.cmd.Parameters.AddWithValue("@StudentCity", city);
        db.cmd.Parameters.AddWithValue("@StudentState", state);
        db.cmd.Parameters.AddWithValue("@StudentPIN", pin);
        db.cmd.Parameters.AddWithValue("@StudentDeptID", dept_id);
        db.cmd.Parameters.AddWithValue("@StudentAddmissionDate", doa);
        db.cmd.Parameters.AddWithValue("@StudentCourseFee", coursefee);
    
        student_details s = new student_details();
     
      //  return db.inupdel("insert into StudentDetails values ('"+name+"','"+address+"','"+city+"', '"+state+"','"+pin+"','"+dept_id+"','"+doa+"','"+coursefee+"')");
    }
}

When ever I am returning the sql it's working fine, but could not able to understand how to return the store procedure to the inupdel() in the db_connection.cs file. Please help. Thanks in advance.