请问下这段代码怎么错了

Question

public string Proc_test(int student_id, int class_id) { string str_conn= string.Format("Data Source=DADI-PC\\MYSQL2008;Initial Catalog=Test;Persist Security Info=True;User ID=sa;Password=mysql2008"); using (SqlConnection conn = new SqlConnection(str_conn)) { conn.Open(); SqlParameter par1 = new SqlParameter("@stu_id", SqlDbType.Int); par1.Value = student_id; SqlParameter par2 = new SqlParameter("@class_id", SqlDbType.Int); par2.Value = class_id; SqlParameter par3 = new SqlParameter("@nun", SqlDbType.VarChar, 50); par3.Direction = ParameterDirection.ReturnValue; SqlCommand cmd = new SqlCommand("proc_test", conn); cmd.CommandType = CommandType.StoredProcedure; cmd.Parameters.Add(par1); cmd.Parameters.Add(par2); cmd.Parameters.Add(par3); cmd.ExecuteNonQuery(); return cmd.Parameters["@nun"].Value.ToString(); } }     ALTER proc [dbo].[proc_test] @stu_id int,@class_id int,@nun varchar(50) outputas begin if exists( select student_str_id from Student where Student_id=@stu_id and Class_id=@class_id) select @nun='true'; else select @nun='flase';end  

Answer 1

你好歹把什么错给贴出来呀

 

 

par3.Direction = ParameterDirection.ReturnValue;

这句，你用的是output参数   这里枚举用错了