Select data using (DATA SET)ds and dt

It is step3 procedure 

protected void btn_select_Click(object sender, EventArgs e)

    {

        Datac c=new datac();

       first f= c.search(Convert.ToInt32(TextBox1.Text));

       TextBox2.Text = Convert.ToString(f.name);

       TextBox3.Text = Convert.ToString(f.course);

       TextBox4.Text = Convert.ToString(f.fee);

        Label1.Text = "record fetched";

    }

It is step4 procedure

Variable class

public class first

{

    public int id{get;set;}

    public string name { get; set; }

    public string course { get; set; }

    public int fee { get; set; }

}

It is step5 procedure

public first searchmain(Int32 ss)

    {

        Int32 sa = ss;

        string querystring= "select * from student where stu_id="+ sa;

         

first f = new first();

             string constring = "Data Source= SHYAM-6E8C5C74B\\SQLEXPRESS  ;initial catalog=college; integrated security=True "

        SqlConnection cn = new SqlConnection(constring);

        SqlDataAdapter da = new SqlDataAdapter(querystring,cn);

        DataSet ds = new DataSet();

        da.Fill(ds);

    

        f.name = Convert.ToString(ds.Tables[0].Rows[0][1]);

        f.course = Convert.ToString(ds.Tables[0].Rows[0][2]);

        f.fee = Convert.ToInt32(ds.Tables[0].Rows[0][3]);

        return f;

    }