贴出相关代码

private void butEnter_Click(object sender, System.EventArgs e)
        { bool bolLog;
            bolLog=true;

            string userName=txtName.Text;            

            //用来存储用户的姓名
            string userPWD=txtPWD.Text;            

            //用来存储用户的密码
            
            OleDbConnection OleDbconn=new OleDbConnection

                ("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\\yonghu.mdb");
            OleDbconn.Open();
            string OleDb="select * from yonghu";   

            //用来存储查询语句
            
            OleDbCommand commnd = new OleDbCommand

                (OleDb,OleDbconn);
            
            OleDbDataReader newOleDbReader = 

                commnd.ExecuteReader();
           while(newOleDbReader.Read())        //循环

           //读取数据库的记录
            {
                //如果用户名和密码与数据库中的记录匹配
                if(newOleDbReader.GetString(0) == 

          userName.Trim() && newOleDbReader.GetString(1) == userPWD.Trim())
                {
                    

            this.DialogResult=DialogResult.OK;
                    MessageBox.Show("登陆成功");    
                    bolLog = true;//实现生命的一个Bool变量
                //则执行登陆成功语句
                    break;
                }

                //如果用户名和密码与数据库中的记录不匹

                     //配
                else
                {
                     bolLog = false;//实现生命的一个Bool变量
                }
            }
            if (bolLog == false) 
            {
                  MessageBox.Show("错误的用户名及密码");              
             }
调试的时候在select语句上出现绿色线.