How to make it my database connection as function and can be share by others

Let's say, i've following ASP.NET with C# code,

MsgAdd.aspx
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public string SQLServerConn = ConfigurationManager.AppSettings["MySQLConn"].ToString();
.....
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private void AddARMsgHdr()
    {       
        SqlConnection con = new SqlConnection(SQLServerConn);
        SqlCommand cmd = new SqlCommand("tfpxPay_InstACMsgHdr", con);
        cmd.CommandType = CommandType.StoredProcedure;
        try
        {
            con.Open();
            SqlParameter pARMsg_Type = new SqlParameter("ARMsg_Type", SqlDbType.VarChar, ...