DataReader的用法

在通常情况下，DataSet与 DataReader可能可以相互代替，当有特定要求时却需要仔细分析，到底使用哪种方式更合适。

用DataReader处理登录表单

private void buttonLogOn_Click(object sender, System.EventArgs e)

        {   

            bool a_accept=false;

            string connectionString="workstation id=localhost;initial catalog=CommuList;user id=sa; pwd=";

            SqlConnection myConnection=new SqlConnection(connectionString);

            SqlCommand myCommand=myConnection.CreateCommand();

            myCommand.CommandText="select * from Users";

            myConnection.Open();

            SqlDataReader myDataReader=myCommand.ExecuteReader();

            while(myDataReader.Read())

                if(myDataReader.GetString(0).Trim()==textBoxUser.Text.Trim() &&

                    myDataReader.GetString(1).Trim()==textBoxPW.Text.Trim())

                        {

                         a_accept=true;

                         break;

                        }

            if(a_accept==true) 

                {  

                    MessageBox.Show("恭喜你可以成功登录！");

                    this.Close();

                }

            else

                {   

                    MessageBox.Show("你的用户名或密码错误，请重新输入！");

                    textBoxUser.Text="";

                    textBoxPW.Text="";

                    textBoxUser.Focus();

                }

        }

        private void textBoxUser_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)

        {  

            if(e.KeyCode.ToString()=="Down" || e.KeyCode.ToString()=="Right"|| e.KeyCode.ToString()=="Enter")

              textBoxPW.Focus();

        }

        private void textBoxPW_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)

        {  

            if(e.KeyCode.ToString()=="Down" || e.KeyCode.ToString()=="Right"|| e.KeyCode.ToString()=="Enter")

                buttonLogOn.Focus();

        }

      }

}