using following c# code, I am trying to get sum of a field "LNOD" type varchar in a variable "mysum"

protected void Button7_Click(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection("Server=SDCHO\\SQLEXPRESS;Database=LoginPage;Trusted_Connection=true");
con.Open();
SqlCommand myCommand2 = new SqlCommand("select sum(lnod) as mysum from LeaveDataTable where ID='212' ", con);
myCommand2.ExecuteNonQuery();
Response.Write('The Sum of LNOD is :' + mysum);
con.Close();
}

please help it is not working