Oracle function is not a procedure or is undefined. Statement ignored

Question

I am trying to call an Oracle function from C# that returns multiple rows but it is not working. Here is the function I am using:

create or replace function return_columns(
   tableName IN varchar
)
return types.ref_c
as
  c_result types.ref_c;
begin
  open c_result for
    select column_name 
      from all_tab_columns
     where table_name = tableName;

  return c_result;
end return_columns;

Here is the type:

create or replace package types
as
  type ref_c is ref cursor;
end;

I am in C# code calling the function like this:

OracleConnection oraConn = new OracleConnection("DATA SOURCE=MySource;PASSWORD=MyPassword;USER ID=MyID");
OracleCommand objCmd = new OracleCommand("MyID.RETURN_COLUMNS", oraConn);
objCmd.CommandType = CommandType.StoredProcedure;

OracleParameter oraParam = new OracleParameter("tableName", OracleType.VarChar);
oraParam.Value = "MY_TABLE";
oraCmd.Parameters.Add(oraParam);

oraConn .Open();

DataTable dt = new DataTable();

OracleDataAdapter ad = new OracleDataAdapter(objCmd);

ad.Fill(dt);

oraConn.Close();

And it keeps returning this error:

'RETURN_COLUMNS' is not a procedure or is undefined ORA-06550: line 1, column 7: PL/SQL: Statement ignored

What is wrong with my Oracle function?

Answer 1

You simply need to define one more parameter, a parameter responsible for return value. Here is an example:

OracleParameter retVal = new OracleParameter("retVal", OracleDbType.RefCursor);
retVal.Direction = ParameterDirection.ReturnValue;

Note #1: The retVal parameter should be added first in the parameter list, otherwise you might receive ORA-00306: wrong number or type of arguments.. error.

 cmd.Parameters.Add(retVal);    -- ReturnValue parameter is being added first 
 cmd.Parameters.Add(tabName);   -- then goes everything else

Note #2: It would be better to use ODP for .NET instead of obsolete and deprecated Microsoft Oracle client (System.Data.OracleClient)

Note #3: Use varchar2 data type instead of varchar in your PL/SQL code. As of now they are synonyms but their behavior might change in the future.