compare current date with a date in database

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C#

ASP.NET

SQL

server

Hi guys,

I'm trying to implement an application for my web site , where I want to discount products 20% in their price which they are older than a year.

So I have a datatable products with columns [id,name,price,date]
with the following code i retrieve the current date and then I try to retrieve the date from my
sql table products and compare with the today date , but i don't now how to compare them and decide if that is an old product?
is this the correct way where i'm trying to do this?
what i shoud change in order to work this?

Thnx in advance!!!

string todaydate = DateTime.Now.ToString("dd/MM/yyyy");

 SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ToString());

        string aSql = "select date from products";
         SqlCommand sqlCommand = new SqlCommand(aSql, con);
     
      
            con.Open();
            using (SqlDataReader read = sqlCommand.ExecuteReader())
            {
                while (read.Read())
                {
                    string date2 = read["date"].ToString();
                    string price = read["price"].ToString();

                    if(todaydate - date2 > )//12months i must writte something here)
                    {
                        int price2 = Convert.ToInt32(price) - ((20/100)*Convert.ToInt32(price));
                    }
                }
                GridView1.DataSource = read;
                GridView1.DataBind();
                read.Close();
                
            }
            con.Close();