C＃调用SP Oracle只返回没有数据的头？

Question

我有：

PROCEDURE GET_1(
  cv_1 OUT SYS_REFCURSOR
)
AS
BEGIN  
  OPEN cv_1 FOR SELECT 1 FROM DUAL; 
END;

PROCEDURE GET_2(
  cv_2 OUT SYS_REFCURSOR
)
AS
BEGIN  
  GET_1(cv_2); 
END;

var conn = new OracleConnection(ConnStr);
conn.Open();
var cmd = new OracleCommand();
cmd.Connection = conn;
cmd.CommandText = "GET_2";
cmd.CommandType = CommandType.StoredProcedure;
cmd.BindByName = true;
var orlPara = new List<OracleParameter>();
var cv_2 = new OracleParameter("cv_2", OracleDbType.RefCursor, ParameterDirection.Output);
orlPara.Add(cv_2);

cmd.Parameters.AddRange(orlPara.ToArray());
var adapter = new OracleDataAdapter(cmd);
var ds = new DataSet();
adapter.Fill(ds);
return ds;

当我在SQL Developer GET_2中运行时，它返回结果，但是当我使用C＃调用GET_2时，只返回没有数据的头，那么我需要做什么？