asp.net - 获取下拉列表中所选项目的值

Question

我添加了项目dropdownlist，当我选择我添加的项目时，它没有显示在Label1. 这是我的代码：

ASPX

<asp:Label ID="Label1" runat="server"></asp:Label> 
<asp:DropDownList ID="drpOne" runat="server" AutoPostBack="true">
        </asp:DropDownList>

VB

Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load

    con.Open()
    If Not IsPostBack Then
        Dim Sql = "SELECT College FROM College"
        cmdAdd = New SqlDataAdapter(Sql, con)
        Dim ds As New DataSet()
        cmdAdd.Fill(ds)

        drpOne.DataSource = ds
        drpOne.DataTextField = "College"
        drpOne.DataValueField = "College"
        drpOne.DataBind()
        drpOne.Items.Insert(0, New ListItem("Please select College", ""))
        drpOne.SelectedItem.Value = "Please select College"
        drpOne.Items.Insert(0, New ListItem("All", ""))
 end if
End Sub

Protected Sub drpOne_SelectedIndexChanged(sender As Object, e As System.EventArgs) Handles drpOne.SelectedIndexChanged
    Label1.Text = drpOne.SelectedItem.Value
End Sub

Answer 1

我还没有检查代码，但尝试这种方式

Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load

    con.Open()
    If Not IsPostBack Then
        Dim Sql = "SELECT College FROM College"
        cmdAdd = New SqlDataAdapter(Sql, con)
        Dim ds As New DataSet()
        cmdAdd.Fill(ds)

        drpOne.AppendDataBoundItems = true
        drpOne.Add(New ListItem("Please select College", ""))//You have passed "Please select College" as text and "" as value in ListItem
        drpOne.Add(New ListItem("All", ""))

        drpOne.DataSource = ds
        drpOne.DataTextField = "College"
        drpOne.DataValueField = "College"
        drpOne.DataBind()

        drpOne.Items.FindByText("Please select College").Selected = true
 end if
End Sub

Protected Sub drpOne_SelectedIndexChanged(sender As Object, e As System.EventArgs) Handles drpOne.SelectedIndexChanged
    Label1.Text = drpOne.SelectedItem.Value
End Sub

Answer 2

drpOne.SelectedItem.Text == "enter the value which you want to search"

Answer 3

DataValueField 必须设置你的主键列Id，我认为CollegeId 就是这样。

drpOne.DataTextField = "College"
        drpOne.DataValueField = "CollegeId"//Must set Integer value for dropdown  item vale