How to return a RefCursor from Oracle function? - oracle

Question

I am trying to execute a user-defined Oracle function that returns a RefCursor using ODP.NET. Here is the function:
CREATE OR REPLACE FUNCTION PKG.FUNC_TEST (ID IN TABLE.ID%type)
RETURN SYS_REFCURSOR
AS
REF_TEST SYS_REFCURSOR;
BEGIN
OPEN REF_TEST FOR
SELECT *
FROM TABLE;
RETURN REF_TEST;
END;
/
I can call this function in Toad (select func_test(7) from dual) and get back a CURSOR. But I need to get the cursor using C# and ODP.NET to fill a DataSet, but I keep getting a NullReferenceException - "Object reference not set to an instance of an object". Here is what I have for that:
OracleConnection oracleCon = new OracleConnection(ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString);
OracleCommand sqlCom = new OracleCommand("select func_test(7) from dual", oracleCon);
sqlCom.Parameters.Add("REF_TEST", OracleDbType.RefCursor, ParameterDirection.ReturnValue);
OracleDataAdapter dataAdapter = new OracleDataAdapter();
dataAdapter.SelectCommand = sqlCom;
DataSet dataSet = new DataSet();
dataAdapter.Fill(dataSet); //FAILS HERE with NullReferenceException
I was able to find lots of info and samples on using stored procedures and ODP.NET, but not so much for returning RefCursors from functions.
EDIT: I do not want to explicitly add input parameters to the OracleCommand object (i.e. sqlCom.Parameters.Add("id", OracleDbType.Int32,ParameterDirection.Input).Value = 7;) as that makes it difficult to implement this as a generic RESTful web service, but I'm reserving it as my last resort but would use stored procedures instead.
Any help is much appreciated!

Answer 1

I think you are missing the sqlCom.ExecuteNonQuery();
also, instead of running the select func_test(7) from dual; lets switch it to run the function and pass in the param
OracleConnection oracleCon = new OracleConnection(ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString);
// Set the command
string anonymous_block = "begin " +
" :refcursor1 := func_test(7) ;" +
"end;";
//fill in your function and variables via the above example
OracleCommand sqlCom= con.CreateCommand();
sqlCom.CommandText = anonymous_block;
// Bind
sqlCom.Parameters.Add("refcursor1", OracleDbType.RefCursor);
sqlCom.Parameters[0].Direction = ParameterDirection.ReturnValue;
try
{
// Execute command; Have the parameters populated
sqlCom.ExecuteNonQuery();
// Create the OracleDataAdapter
OracleDataAdapter da = new OracleDataAdapter(sqlCom);
// Populate a DataSet with refcursor1.
DataSet ds = new DataSet();
da.Fill(ds, "refcursor1", (OracleRefCursor)(sqlCom.Parameters["refcursor1"].Value));
// Print out the field count the REF Cursor
Console.WriteLine("Field count: " + ds.Tables["refcursor1"].Columns.Count);
}
catch (Exception e)
{
Console.WriteLine("Error: {0}", e.Message);
}
finally
{
// Dispose OracleCommand object
cmd.Dispose();
// Close and Dispose OracleConnection object
con.Close();
con.Dispose();}
this is based on the example ODP that can be found # %ora_home%\Client_1\ODP.NET\samples\RefCursor\Sample5.csproj
If you want to avoid (for better or worst!) the custom built param collection for each proc/function call you can get around that by utilizing anonymous blocks in your code, I have ammended (once again untested!) the code above to reflect this technique.
Here is a nice blog (from none other than Mark Williams) showing this technique.
http://oradim.blogspot.com/2007/04/odpnet-tip-anonymous-plsql-and.html