using System;
using System.Collections.Generic;
using System.Text;

using System.Data;                       
using System.Data.Sql;         
using System.Data.SqlClient;   
using System.Data.SqlTypes;     
using System.Data.Odbc;

using System.Configuration;     

namespace StudentManagementSystem
{
    class c_MDIManagement      
    {
        string str_username;

        int i_userType;   

        SqlConnection conn = new SqlConnection("server=.;pwd=sun;user id=sa;database=SIM");

        SqlCommand cmd = new SqlCommand();

        SqlDataReader dr;

        public c_MDIManagement(string str)
        {
            str_username = str.Trim();
        }

        public int user_Type()      
        {
            try
            {
                conn.Open();

                string str_UserType = "select t_UserType from tb_UserInfo where t_UserName='" + str_username + "'";      

                = str_UserType;

                cmd.Connection = conn;
               
                dr = cmd.ExecuteReader();

                if (dr.Read())
                {
                    i_userType = Convert.ToInt32(dr["t_UserType"].ToString());
                }
                else
                {
                    i_userType = 111;
                }
                conn.Close();
            }
            finally
            {
                conn.Close();
            }
            return i_userType;
        }
    }
}

我应改返回的是数据库中的t_UserType，而实际返回的是111或是0,这是哪的错？

if (dr.Read())
应该是没有数据读吧？才会到
else
                {
                    i_userType = 111;
                }
返回0的话应该是try的地方报错了，直接了 return i_userType;
i_userType没有初始值所以是0

你设一下断点，跟一下，看看

你的数据库里查询出来的是空值，发生异常
呵呵