How to dynamically connect to multiple Databases at runtime by changing connection string in ASP.Net

Put the connection string in web.config say and then access it as following

    protected void ddlConnections_SelectedIndexChanged(object sender, EventArgs e)
    {
        string conString = "";
        if (ddlConnections.SelectedItem.Value == "2013")
        {
            conString = ConfigurationManager.ConnectionStrings["ConString_2013"].ConnectionString;
        }
        if (ddlConnections.SelectedItem.Value == "2014")
        {
            conString = ConfigurationManager.ConnectionStrings["ConString_2014"].ConnectionString;
        }
        SqlConnection con = new SqlConnection(conString);
        con.Open();
    }