求解释代码意思
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
  '在此处放置初始化页的用户代码
  If Not IsPostBack Then
  BindData()
  End If
  End Sub
  Private Sub BindData()
  Dim obj As DBController = New DBController
  obj.BindListBox("select * from BookInfo order by BookID asc", BookList)
  obj.Close()
  End Sub

  Private Sub BookList_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles BookList.SelectedIndexChanged
  Dim BookID As String = BookList.SelectedValue.ToString.Trim
  Dim sqlstr As String = "select * from BookInfo where BookID =" + BookID
  Dim obj As DBController = New DBController
  obj.Open()
  Dim myreader As SqlDataReader = obj.ExecReaderSql(sqlstr)
  If myreader.Read Then
  txtBookName.Text = myreader("BookName")
  txtPubName.Text = myreader("PubName")
  txtBookAuthor.Text = myreader("BookAuthor")
  DpStyle.SelectedValue = myreader("BookStyle")
  txtUploadDate.Text = myreader("UploadDate")
  txtPubDate.Text = myreader("PubDate")
  txtSeries.Text = myreader("Series")
  txtSubject.Text = myreader("Subject")
  DpLanguage.SelectedValue = myreader("Language")
  txtISBN.Text = myreader("ISBN")
  txtSearchNO.Text = myreader("SearchNO")
  DpBookState.SelectedValue = myreader("BookState")
  txtPrice.Text = myreader("Price")
  txtBarCode.Text = myreader("BarCode")
  End If
  obj.Close()

------解决方案--------------------

VB.NET code

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
  '在此处放置初始化页的用户代码
  If Not IsPostBack Then
  BindData()'首次加载时绑定数据
  End If
  End Sub
  Private Sub BindData()’绑定BookList对象的方法
  Dim obj As DBController = New DBController
  obj.BindListBox("select * from BookInfo order by BookID asc", BookList)
  obj.Close()
  End Sub

  Private Sub BookList_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles BookList.SelectedIndexChanged
  Dim BookID As String = BookList.SelectedValue.ToString.Trim'取选中项的值
  Dim sqlstr As String = "select * from BookInfo where BookID =" + BookID'根据取值拼结sql字符串
  Dim obj As DBController = New DBController
  obj.Open()
  Dim myreader As SqlDataReader = obj.ExecReaderSql(sqlstr)
  If myreader.Read Then'取出记录集，若存在，则对下面的一系列控件赋值
  txtBookName.Text = myreader("BookName")
  txtPubName.Text = myreader("PubName")
  txtBookAuthor.Text = myreader("BookAuthor")
  DpStyle.SelectedValue = myreader("BookStyle")
  txtUploadDate.Text = myreader("UploadDate")
  txtPubDate.Text = myreader("PubDate")
  txtSeries.Text = myreader("Series")
  txtSubject.Text = myreader("Subject")
  DpLanguage.SelectedValue = myreader("Language")
  txtISBN.Text = myreader("ISBN")
  txtSearchNO.Text = myreader("SearchNO")
  DpBookState.SelectedValue = myreader("BookState")
  txtPrice.Text = myreader("Price")
  txtBarCode.Text = myreader("BarCode")
  End If
  obj.Close()'关闭数据库对象