Question

我尝试用ASP中的DropDownList绑定国家，州和城市。 NET使用VB.NET。问题是当我选择国家时，没有显示与国家有关的国家名单。我使用MS Access 2003作为数据库，这是我的表格＆amp;代码

Country Table

创建表格国家/地区（ CountryID Int主键， CountryName Varchar（30））

CountryState表

创建表countryState （ StateID Int主键， CountryID Int外键引用国家（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

Answer 1

因为CountryID是一个整数，所以在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注入攻击创建低挂果。

使用ASP中的DropDownList绑定国家，州和城市。 NET使用VB.NET

1 个答案: