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我尝试在 ASP 中使用 DropDownList 绑定国家、州和城市。NET 使用 VB.NET。问题是当我选择国家时，没有显示与国家相关的国家列表。我使用 MS Access 2003 作为数据库，这是我的表格和代码

Country Table

创建表 Country ( CountryID Int Primary Key, CountryName Varchar(30) )

国家状态表

创建表 countryState (StateID Int Primary Key, CountryID Int Foreign Key References Country(CountryID), State Varchar(30))

 Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    cnnOLEDB.ConnectionString = strConnectionString
    If Not IsPostBack Then
        Bind_ddlCountry()
    End If
End Sub
Public Sub Bind_ddlCountry()
    Dim cnnOLEDB As New OleDbConnection(strConnectionString)
    cnnOLEDB.Open()
    Dim cmd As New OleDbCommand("SELECT CountryID,CountryName FROM Country", cnnOLEDB)
    Dim dr As OleDbDataReader = cmd.ExecuteReader()
    ddlcountry.DataSource = dr
    ddlcountry.Items.Clear()
    ddlcountry.Items.Add("--Please Select country--")
    ddlcountry.DataTextField = "CountryName"
    ddlcountry.DataValueField = "CountryID"
    ddlcountry.DataBind()
    cnnOLEDB.Close()
End Sub

Public Sub Bind_ddlState()
    Dim cnnOLEDB As New OleDbConnection(strConnectionString)
    cnnOLEDB.Open()
    'Dim cmd As New OleDbCommand("SELECT StateID, State FROM CountryState", cnnOLEDB)
    Dim cmd As New OleDbCommand("SELECT StateID, State FROM CountryState WHERE CountryID='" & ddlcountry.SelectedValue & "'", cnnOLEDB)
    Dim dr As OleDbDataReader = cmd.ExecuteReader()
    ddlstate.DataSource = dr
    ddlstate.Items.Clear()
    ddlstate.Items.Add("--Please Select state--")
    ddlstate.DataTextField = "State"
    ddlstate.DataValueField = "StateID"
    ddlstate.DataBind()
    cnnOLEDB.Close()

End Sub
Protected Sub ddlcountry_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs) Handles ddlcountry.SelectedIndexChanged
    Bind_ddlState()
End Sub
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1 回答 1

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因为 CountryID 是一个整数，所以 SQL 查询的 WHERE 子句中不需要单引号。

...WHERE CountryID = " & ddlcountry.SelectedValue, cnnOLEDB)

另一个注意事项 - 通常，您应该始终参数化您的变量。否则，您正在为潜在的 SQL 注入攻击创造低垂的果实。

于 2012-10-11T06:19:19.283 回答