How can I create a Class/Method

Question

Hello,

I have this connection string code below;

string conn = ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString.ToString();
            SqlConnection cn;
            cn = new SqlConnection(conn);
            cn.Open();

How can I create a Class/Method to be able to call just a string or variable whenever I need this connection strings on my code page?

I hope my question is clear? Thanks for helping in advance.