无法从下拉列表中获取值 [英] Cannot get the value from the drop down list

问题描述

我使用DisplayBusRouteID（）从数据库中分配项目。当我使用ddlLocation_SelectedIndexChanged（）方法从ddlLocation中选择项时，lblBusTicketPrice不起作用。有什么问题？

I use DisplayBusRouteID() assign item from the database. When I use ddlLocation_SelectedIndexChanged() method to select the item from the ddlLocation, the lblBusTicketPrice does not work. What is the problem ?

protected void DisplayBusRouteID()
{
   DataClassesDataContext db = new DataClassesDataContext();

   var query = from s in db.BusRoutes
         select s;

   ddlLocation.DataSource = query;
   ddlLocation.DataTextField = "BusRouteID";
   ddlLocation.DataBind();
       
}
 protected void ddlLocation_SelectedIndexChanged(object sender, EventArgs e)
{
   lblBusTicketPrice.Text = "abc";
}

推荐答案

设置

autopostback="true"

下拉菜单... :)

of dropdown...:)

protected void DisplayBusRouteID()
{
   DataClassesDataContext db = new DataClassesDataContext();
 
   var query = from s in db.BusRoutes
         select s;
 
   ddlLocation.DataSource = query;
   ddlLocation.DataTextField = "BusRouteID";
  ddlLocation.DataValueField = "BusRouteID";
   ddlLocation.DataBind();
       
}
 protected void ddlLocation_SelectedIndexChanged(object sender, EventArgs e)
{
   lblBusTicketPrice.Text = "abc";
}

确保您的dropdownlist标签具有属性 AutoPostBack =true和页面加载方法如下..

make sure your dropdownlist tag has the attribute AutoPostBack="true" and page load method as below..

<asp:dropdownlist id="ddlLocation" autopostback="true" runat="server" onselectedindexchanged="ddlLocation_SelectedIndexChanged" xmlns:asp="#unknown"></asp:dropdownlist>

protected void Page_Load(object sender, EventArgs e)
       {
           if (!Page.IsPostBack)
           {
               // make sure all your initialisation andloading methods are called is in this block.
               // not outside this block

           }
       }</pre>

将ddlLocation的autopostback属性设置为true

Set autopostback property of ddlLocation to true

<asp:DropDownList ID="ddlLocation" runat="server" AutoPostBack="True"                onselectedindexchanged="ddlLocation_SelectedIndexChanged">
</asp:DropDownList>

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