Can we have 2 different Oracle Dependency from 2 different database in a single asp.net application

Question

I am developing a asp.net web api application where I'm trying to get oracle database change notification in c#. But when I am Initializing 1 oracle dependency, everything is working as expected but when I am trying to Initialize 2 oracle dependency from 2 different oracle database, I am getting an error "'This operation requires the objects to use the same connection'"

var cmd = new OracleCommand("SELECT EMPNO FROM EMP r WHERE rownum <= 1 Order by EMPNO Desc", con1);
con1.Open();
cmd.AddRowid = true;
var dep = new OracleDependency(cmd);
dep.OnChange += new OnChangeEventHandler(dep_OnChange);
DataTable dt = new DataTable();
dt.Load(cmd.ExecuteReader());

var cmd2 = new OracleCommand("SELECT EMPNO FROM EMP2 r WHERE rownum <= 1 Order by EMPNO Desc", con2);
con2.Open();
cmd2.AddRowid = true;
var dep2 = new OracleDependency(cmd2);
dep2.OnChange += new OnChangeEventHandler(dep2_OnChange);
DataTable dt2 = new DataTable();
dt2.Load(cmd2.ExecuteReader());

Answer 1

firstly this step by step guide may resolve your issue: Oracle Dependency Guide

Secondly, this is also another work around you can use to do your job. Yes there can be. Your Database layer should contain 2 classes which will connect to the respective database. Plus don't use ExecuteReader, instead use DataAdapter because it handles Connection.Open(), Close(), Dispose() itself.

for example

DATABASE1.CS

public class Database1
{
    string sCon = string.Empty;
    OracleConnection OraCon;
    protected string query = string.Empty;
    public Database1()
    {
       sCon = "Data Source=(DESCRIPTION =(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST = 1.1.1.1)(PORT = 12345)))(CONNECT_DATA =(SID = SIDNAME)));User ID=username;Password=pass;";
       OraCon = new OracleConnection(sCon);
    }

    protected DataTable FillDataTableByParam(OracleParameter[] param)
    {
        DataTable oDT = new DataTable();
        OracleCommand OraCom = new OracleCommand(query, OraCon);
        OraCom.Parameters.AddRange(param);
        new OracleDataAdapter(OraCom).Fill(oDT);
        query = "";
        return oDT;
    }
}

DATABASE2.CS

public class Database2
{
    string sCon = string.Empty;
    OracleConnection OraCon;
    protected string query = string.Empty;
    public Database2()
    {
       sCon = "Data Source=(DESCRIPTION =(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST = 1.1.1.1)(PORT = 12345)))(CONNECT_DATA =(SID = SIDNAME2)));User ID=username;Password=pass;";
       OraCon = new OracleConnection(sCon);
    }

    protected DataTable FillDataTableByParam(OracleParameter[] param)
    {
        DataTable oDT = new DataTable();
        OracleCommand OraCom = new OracleCommand(query, OraCon);
        OraCom.Parameters.AddRange(param);
        new OracleDataAdapter(OraCom).Fill(oDT);
        query = "";
        return oDT;
    }
}

But you can also keep 1 class in your Database Layer making it accessible for 2 databases, it would look something like this:

public class DatabaseLayer
    {
        string sCon = string.Empty;
        OracleConnection OraCon;
        protected string query = string.Empty;
        public DatabaseLayer(string DataBaseSecureName)
        {
           if(DataBaseSecureName ==  "One")
           {
            sCon = "Data Source=(DESCRIPTION =(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST = 1.1.1.1)(PORT = 12345)))(CONNECT_DATA =(SID = SIDNAME)));User ID=username;Password=pass;";
           }
           else if (DataBaseSecureName ==  "Second")
           {
            sCon = "Data Source=(DESCRIPTION =(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST = 1.1.1.1)(PORT = 12345)))(CONNECT_DATA =(SID = SIDNAME2)));User ID=username;Password=pass;";
           }

           OraCon = new OracleConnection(sCon);
        }

        protected DataTable FillDataTableByParam(OracleParameter[] param)
        {
            DataTable oDT = new DataTable();
            OracleCommand OraCom = new OracleCommand(query, OraCon);
            OraCom.Parameters.AddRange(param);
            new OracleDataAdapter(OraCom).Fill(oDT);
            query = "";
            return oDT;
        }
    }

You can add a method to the Classes/Class i wrote above with logic to return notification on change of connection, and then use it as it pleases you.