store procedure to insret all the data into database including dropdownlist

the data is not storing inside the database

protected void Button1_Click(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=demo1;Integrated Security=True");
con.Open();



int a = Convert.ToInt32(TextBox1.Text);
int b = Convert.ToInt32(TextBox2.Text);


if (DropDownList1.Text == "add")
{
int sum = (a + b);
Label1.Text = Convert.ToString(sum);
dat.Text = DateTime.Now.ToString();

}
if

(DropDownList1.Text == "sub")
{
int sub = (a - b);
Label1.Text = Convert.ToString(sub);
dat.Text = DateTime.Now.ToString();
}
if
(DropDownList1.Text == "mul")
{
int mul = a * b;
Label1.Text = Convert.ToString(mul);
dat.Text = DateTime.Now.ToString();
}
if
(DropDownList1.Text == "div")
{
decimal div = a / b;
Label1.Text = Convert.ToString(div);
dat.Text = DateTime.Now.ToString();
}

SqlCommand cmd = new SqlCommand();

cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandText = "p";

cmd.Parameters.AddWithValue("@firsttno", TextBox1.Text);
cmd.Parameters.AddWithValue("@secondno", TextBox2.Text);
cmd.Parameters.AddWithValue("@operation", DropDownList1.Text);
cmd.Parameters.AddWithValue("@result", Label1.Text);
cmd.Parameters.AddWithValue("@optime", dat.Text);
cmd.Connection = con;
cmd.ExecuteNonQuery();

con.Close();

}
}
}