现在对我有用.错误是我已将参数"Id"声明为varchar2.但是我没有给它任何尺寸.现在，我已经声明了参数的最大大小及其正常工作.

It is working for me now. Mistake is I have declared a parameter "Id" as varchar2. but I didn't give any size to that. Now I have declared max size to the parameter and its working fine.

 cmd_chk.Parameters.Add("id", OracleDbType.Varchar2,32767).Direction = ParameterDirection.Output;