How to return a RefCursor from Oracle function?

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