Petapoco - Getting return from Oracle function

I'm running into the same problem as outlined in this post:  
http://stackoverflow.com/questions/35113140/executing-oracle-function-and-getting-back-a-return-value 

I can do this in my Toad client successfully:
declare result varchar2(30);
BEGIN 
  result:=WEBUSER.F_UpdateParticipant(json input_goes here);
  dbms_output.put_line(result); 
END;

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and get the return value shown in dbms_output.
This function returns:
{"Success":true} 

or 

{"Success":false} 

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But I cannot get the output returned to Petapoco. I've also tried using output params like this:
var result = new Oracle.ManagedDataAccess.Client.OracleParameter("result",Oracle.ManagedDataAccess.Client.OracleDbType.Varchar2, System.Data.ParameterDirection.Output);
var sql = "DECLARE result VARCHAR2(30);" + 
          "BEGIN "+
          "    @0:=WEBUSER.F_UpdateParticipant(@1);" +
          "END;";
_db.db.Execute(sql, result, json);
res = result.ToString();

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AND
var result = new Oracle.ManagedDataAccess.Client.OracleParameter("result",Oracle.ManagedDataAccess.Client.OracleDbType.Varchar2, System.Data.ParameterDirection.Output);
var sql = "DECLARE result VARCHAR2(30);" + 
          "BEGIN "+
          "    @result:=WEBUSER.F_UpdateParticipant(@1);" +
          "END;";
_db.db.Execute(sql, result, json);
res = result.ToString();

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Yes, used both Execute and ExecuteScalar with same results.  
I don't really want to go back to the ADO way of doing these types of queries.
LVL 27
Eddie ShipmanAll-around developerAsked:
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Guy Hengel [angelIII / a3]Billing EngineerCommented:
I think you can make your life much simpler ...
select WEBUSER.F_UpdateParticipant(@1) from dual;

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and don't use the parameter stuff, but a plain "ExecuteScalar" method in "db", though I don't know what "_db" and "_db.db" objects are ...

object res = _db.db.ExecuteScalar(sql, json);

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Eddie ShipmanAll-around developerAuthor Commented:
Guy,
The @0 is the first parameter in the parameters list in the function call, which is json, If I use @1, I get this error: Specified argument was out of the range of valid values.
I have already tried this this way too, but I MUST get the return value from the function call.
Doing it like above (with @0) returns this error: ORA-00911: invalid character

_db.db is the PetaPoco Db connector.

Do you have any other suggestions?
Eddie ShipmanAll-around developerAuthor Commented:
Ok, I've been able to get it to successfully update the record, however, I cannot get the return value at all.
string sql = "DECLARE res VARCHAR2(30); BEGIN return WEBUSER.F_UpdateParticipant(@0); END;";
object res  = _db.db.ExecuteScalar<string>(sql, json);

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But res is null because I cannot return anything from the "procedure", I get this if I try:
ORA-06550: line 1, column 33:
PLS-00372: In a procedure, RETURN statement cannot contain an expression
ORA-06550: line 1, column 33:
PL/SQL: Statement ignored
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Guy Hengel [angelIII / a3]Billing EngineerCommented:
this should do:
string sql = "select WEBUSER.F_UpdateParticipant(@0) FROM DUAL";
string res  = _db.db.ExecuteScalar<string>(sql, json);

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Eddie ShipmanAll-around developerAuthor Commented:
Not exactly... Besides an Update, there is also an insert in the function so we get the cannot perform a DML operation inside a query exception.
Guy Hengel [angelIII / a3]Billing EngineerCommented:
Eddie ShipmanAll-around developerAuthor Commented:
I'll have to ask our Oracle developer about this one, for sure...
Eddie ShipmanAll-around developerAuthor Commented:
Ok, after adding that to the function, I'm getting this:
ORA-06519: active autonomous transaction detected and rolled back
ORA-06512: at "WEBUSER.F_UPDATEPARTICIPANT", line 153

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I'm going to talk to the Oracle developer about how to rewrite this function to work correctly as it is, in my opinion, kind of clunky and stupid in the way it was written.
Eddie ShipmanAll-around developerAuthor Commented:
Ok, Guy, I have a solution. I thought I had tried it before from looking at my previous posts. However, when I wrote the SQL, I included the wrapped version and that is what caused the exception, the wrapped sql. If the SQL is written like below, it works, perfectly.

public string UpdateParticipant(ParticipantUpdate Participant)
{
    string ret = "";
    IsoDateTimeConverter dt = new IsoDateTimeConverter();
    dt.DateTimeFormat = "MM-dd-yyyy"; // we must have this format for our dates
    string json = JsonConvert.SerializeObject(Participant, dt);
    // Creating this output parameter is the key to getting the info back.
    var result = new OracleParameter
    {
        ParameterName = "RESULT",
        Direction = System.Data.ParameterDirection.InputOutput,
        Size = 100,
        OracleDbType = OracleDbType.Varchar2
    };
    // Now, setting the SQL like this using the result as the output parameter is what does the job.
    string sql = $@"DECLARE result varchar2(100); BEGIN  @0 := WEBUSER.F_UpdateParticipant(@1); END;";
    var res = _db.db.Execute(sql, result, json);

    // Now return the value of the Output parameter!!

    ret = result.Value.ToString();
    return ret;
}

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Guy Hengel [angelIII / a3]Billing EngineerCommented:
interesting ...
Eddie ShipmanAll-around developerAuthor Commented:
Yes, for some reason, I kept getting some stupid error from Oracle about invalid character "". so I rewrote the SQL without the wrapping and viola!!
Well, I also redid the output parameter creation, too.
Eddie ShipmanAll-around developerAuthor Commented:
Self-answered
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